Answer: It's Jaune vs Cinder
Keep in mind this is just a general overview and a summary.
I know everyone hates Jaune but bear with me here.
Now, I didn't write out each explicit encounter(well I started to but it was taking too long so I got rid of it) and I removed any details I had on the final fight hoping you guys would just get the gist on what the story I had in mind is supposed to accomplish. Theres probably some minor details here and there that don't make sense and thats understandable because a lot of nuance is skipped over and you can't see what I'm seeing in my head as I imagine this conflict.
Just know that there is in fact a legitimate reason for everything I say/suggest.
Keep in mind, the only thing I am trying to convey is that there is far more story to pull out of the Jaune vs Cinder conflict than there is the Ruby vs Cinder conflict. That this is the better narrative to spin based on what we already have. Thats all this is meant to accomplish.
So enjoy my half-assed ramblings.
Why Ruby vs Cinder Fails
It's very clear that Cinder & Ruby are being set up as rivals. Silver & Gold. Naive cute youth, vs Cunning mature beauty etc. Not to mention Cinder's very typical "Villain obsessed with the Hero" shtick. Though I'd like to argue(and I'm sure I'm not the first) that their conflict doesn't really work. The narrative tries to set up some sort of a beef between them, but ultimately it just falls flat. We know that Cinder really really hates Ruby.....But why? Because she scarred her face? This comes off as really shallow and isn't something that the audience can really invest in. Now you could argue that this is done in an attempt to make Cinder seem vain or petty, but without any backstory the audience isn't able to be invested in her reasons. Because again, it's superficial. On the flip side, what is Ruby's reason for despising Cinder? Because she's evil? Because she hurt her friend? Again, these are incredibly superfical reasons. It comes off as "I'm good and you're evil therefore I hate you". It can be seen as nothing more than a good guy who hates a bad guy for being bad, and a bad guy who hates a good guy for being good. Not to mention, Ruby hating Cinder for killing Pyrrha is hardly believable in the first place due to the fact that she has hardly spent any time with Pyrrha whatsoever. Without any deep seated emotion behind them or layers to this conflict it will always come off as empty. A vapid and contrived good guy vs bad guy beef loosely concocted to make Cinder hate our main Hero and nothing more. It's all very half-assed.
However the conflict between Juane and Cinder has far more story potential. From an emotional standpoint it just works. Jaune had strong feelings for Pyrrha be they romantic or otherwise and thus unlike Ruby it gives him ample reason to truly despise Cinder. This alone is already enough reason to be emotionally invested in the conflict as we have watched Jaune and Pyrrha grow closer over the course of Season 1 only to have her be brutally murdered by Cinder. Jaune's feelings of weakness, self-doubt, guilt, and anger are all heavy emotions brought about by Cinder's actions and we perfectly understand why he feels the way he feels. His animosity towards Cinder is only stoked knowing she feels no remorse over her actions and in fact practically forgot about it. As such we genuinely want to see Jaune get revenge for Pyrrha and make up for his failure at the end of Volume 3. So already when looking at just Jaune's side of things we find that his motivations for hating Cinder make perfect sense due to the emotional weight behind them. But what could make Cinder care enough about Jaune to hate him like she does Ruby?
Values in Conflict
"Great drama is not the product of two individuals butting heads; it is the product of the values and ideas of the individuals going into battle. It's conflict between characters and their values. A good opponent has a set of beliefs that come under assault as well. The beliefs of the hero have no meaning, and do not get expressed in the story, unless they come into conflict with the beliefs of at least one other character, preferably the opponent. The actions of the hero and the opponent are based on a set of beliefs, or values. These values represent each character's view of what makes life good. In the best stories, the values of the opponent come into conflict with the values of the hero. Through that conflict, the audience sees which way of life is superior. Much of the power of the story rests on the quality of this opposition.
-John Truby, The Author of The Anatomy of Story
Parallels: First when looking at their characters they're both very similar in some respects. Especially in terms of their goals. In Volume 3 Episode 7 opens with Cinder stating that she wants to be Strong, Feared, and Powerful. From this it can be inferred that there was indeed a time where she was not those things. Why else would she desire them? It was because she did not have them. Therefore, once upon a time Cinder was weak, pathetic, and powerless. Her semblance also hints at this as it really seems rather pathetic compared to most. It's barely anything that could provide an advantage in combat. I wouldn't be surprised if her power was once considered worthless or even outright unfit for combat. Basically from this we can conclude she was an individual who was in a situation where she constantly felt weak and helpless and because of that weakness she desired power so strongly that she would do anything for it. Even her name which has been implied to be fake and something she invented on her own hints at the idea that she hated the person she was and wanted to become someone else entirely. Now, similarly Jaune has also always been considered a weakling. A joke. A goofball nobody, that no one ever takes seriously. As we know from Volume 1 this is something Jaune is fully aware of and he despises it. He hates being pathetic. Weak. Thus, he desires to be a Hero. Someone he can respect. So much so that he'd forge his transcripts and infiltrate the most prestigious Huntsmen School in the world. He'd go to such drastic measures as to commit a crime of this caliber if it meant taking a step towards his dream. As such if were to give them a conflict: Cinder's reason for hating Jaune could be that he is a reminder of what she used to be. A living breathing remnant of that pathetic weakling she once was. Thus looking at him disgusts her as he symbolizes her past self, the identity she tried to forget that keeps coming back to haunt her. So having Jaune serve as a reminder of her own weakness will be the start of her wanting to see him dead just as much as Ruby.
But how will their conflict be structured? Since RWBY is an anime, or more specifically an honorary shounen considering it's place in Jump. Lets use a bit of shounen storytelling. Shounen's most prominent writing technique is one where the fights act as Character Arcs in and of themselves. Now, matching one's internal struggle with the external one is nothing new or revolutionary but shounen battle manga have unquestionably mastered the technique. Every fight tells a story and can even sometimes be considered the "Hero's Journey" in miniature. Often acting as clashes of not just personality, but ideologies, and are used to explore the themes of the narrative. The main thing I'm pointing out with this analysis is how fights can and should be written. Fights can be far more than a mere spectacle of flashy movements and abilities. I have another conflict in mind for Jaune to occur before this one using this same form of storytelling to help him get over his lack of self-worth but for now, with this in mind lets just imagine that each of their fights/clashes/encounters spurs on development in the two culminating in a final fight that concludes the story arcs of both characters.
Ambition: Both characters clearly possess great aspirations and ambition. Now I know Ambition is a word people like to tie to Villains. Deeming them selfish because of it, whereas the Heroes are portrayed as "selfless" doing things for the sake of others rather than themselves. However theres nothing wrong with having an Ambition. It's not an evil thing in it itself. Nor is it synonymous with greed. It's perfectly normal to have goals and to work hard towards achieving them. Thats all Ambition is. However the difference is in how you go about achieving those goals. Sometimes the hero and the villain are basically the same except for the fact that each took a single step in a different direction. Thus, one layer of this potential conflict between Jaune and Cinder can be about Ambition and how each character represents the flipside in what it means to persue a goal. Now their goal in itself is somewhat similar. They both seek power and strength but for different reasons. While for both of them it is on some level a quest for self-worth, Cinder desires largely for the sake of having it. So that she can inspire fear. Jaune desires strength so that he can protect those close to him and to have the ability to help those who need it. Where Cinder is ruthless. Jaune is Kind and Compassionate. Where Cinder uses the people around her like tools for her success. With Jaune we see that his support system on the latter to success is built on friendship and mutual respect. Cinder tears down those around her using them as stepping stones to achive her goals whereas Jaune holds up those around him and they eagerly do so for him in turn. Cinder may have worked hard but she gains strength by stealing from others whereas Jaune simply works hard and his power is one that literally allows him to give power to others instead of taking it. And Lastly, where Cinder's actions are clearly rooted in some deep seated hatred. Jaune is motivated by love. Or at least the memory of the woman who once loved him.
Destiny: Another layer to the fight could involve Cinder's belief in Destiny. Putting that empty one-liner of hers to good use we can pit Cinder's Destiny against Jaune's Hard Work in a clash of ideals. A thematic clash of being Self-Made vs Predetermined Fate. Jaune's position in this thematic conflict being that the person you turn yourself into is entirely up to your own actions. Not Fate. Regardless or who they are or where they came from it is their actions that brought them here. This should involve Jaune showcasing the techniques he's trained his ass off for pitted against the powers Cinder has ruthlessly stolen while under the belief that this is her Destiny. As an added motivation Jaune could be written with some animosity towards the concept of Fate and Destiny as it was in part what led Pyrrha to her doom. Leaving him with a desire to see this mentality crushed. During their final fight thanks to his training with Ozpin, Jaune has reached his true potential and his newfound strength forces her to concede that the previously untalented nobody is now not only the stronger fighter but also the stronger person. With Cinder ultimately coming to the conclusion that she could have been anyone she wanted to but has willingly turned herself into nothing more than a monster. A beast to be put down. And she had no one to blame but herself. Hers was a path of self-destruction where Jaune's path was one of self-overcoming. Having triumphed over his own weaknesses and short-comings whereas Cinder merely succumbed to them. Jaune's victory shouldn't simply be in defeating her or watching her die. He should utterly destroy everything that she believes in. Proving that everything she did to achieve her goals was worthless. That everything she did uptil now meant absolutely nothing.
Ozpin & Salem: Whats more, another layer to this fight could be to depict the difference in ideals between Ozpin and Salem. I've always been curious as to who would train Jaune. After all he is the weakest but the one with the most potential and storywise it just makes sense to bring him up to the level of everyone else so that he's not a hindrance on the battlefield. But in regards to training I've always had in mind that either Ozpin or one of Ozpin's former allies someone who had previously fought against Salem but then dropped out of the pointless battle would be the one to assist him. While I may prefer the latter, despite my preferences I will admit that Ozpin makes the most sense. It's far more appropriate that both Ozpin and Jaune; the two people who experienced the biggest failings during the Fall of Beacon come together to correct the mistakes they made. Both of their failures being tied directly to Cinder it makes sense that their combined effort should be eventually what put her down. With Ozpin seeing Jaune's immense desire to overcome Cinder he finally decides to train him personally to aid in his success as well as make up for his own mistakes. Seen from this perspective it's hard to imagine how Ruby even has a stake in this conflict at all. Cinder's defeat should mean something for characters involved and seeing Cinder defeated should mean the most to the man who failed to protect his school and the boy who failed to protect his partner. That way the victory is actually emotionally impactful because of how personal the victory is to those who had a hand in it. You can also think of this as being similar to Deku & All Might's situation. Remember Ozma is basically THE Original Hero. So we have a young boy whose always wanted to be a Great Hero being trained by the former Greatest Hero there ever was. Thus, adding a new twist to the fight so that now it's a battle between the boy trained by Ozpin and the girl trained by Salem. Both Salem and Ozpin have raised up two youths who represent their ideals and the winning side will essentially be the ones to inheret the world. Not only would this conflict be about leaving the world to the next generation but also through these two individuals be a battle that asks the question of what ideology will decide the future. In addition to this, Jaune and Cinder could be used to mirror the conflict between Ozpin and Salem. Acting as a microcosm of their grander conflict. We have this generation's new Hero a White Knight attempting to save a beautiful Princess(Cinderella) from destroying herself on the path of Evil. Just as Ozpin tried to do years ago with Salem but failed. Here we can have Jaune succeed where his Master had failed.
So heres a quick and shortened Summary of how I see such a conflict playing out: Jaune, no longer grieving over Pyrrha is now using her death as inspiration to become the Hero he dreamed about. He will no longer be treating his life as if it had no value. Pyrrha did not sacrifice hers so that he could die pointlessly. That would make her a fool who died for nothing. If he died then Pyrrha will have wasted her time on him. Death is not an apology. He makes an oath that he is going to live. That he would repay her sacrifice with success. With victory. By becoming the greatest Huntsmen he could possibly be. And save as many lives as possible in the process. He would do it too. Remember an Arc never goes back on their word. But the first step to that, would be defeating her killer. He would seek to surpass and overcome Cinder. Rectifying his first and greatest failure. He attacks her everytime he sees her. He loses every time but each fight he comes back just a little better than before. He won't stop coming back either. No matter how many times she seemingly gets rid of him Jaune Arc always comes back. Whenever he is not on screen he is busy training. With a new move or a new trick here or there and gradually he begins to become a real nuisance to Cinder. Now, remember from Her perspective Jaune represents her past self. Or rather a better version of her that was weak and powerless yet still striving to be strong and through effort is slowly beginning to achieve it. Though not through the methods she currently uses. This is important because Jaune's consistent interactions with Cinder will start to affect her development. Causing her to reflect on her actions and question if the path she's on is the right one(note: we did see a brief glimpse of this when Cinder was watching Tyrian attack that Ursa like a madman). After all if the man she once deemed a weak failure can continue to grow like this what had been stopping her from simply doing the same? He had not sacrificed his limbs and turned himself into a monster. Did she really need to be ruthless? or even join up with Salem to achieve her goals? Thoughts like this combined with Cinder having flashbacks to her past whenever she sees Jaune suddenly makes him someone she must kill at all costs due to him drudging up old memories, making her question everything she's done up until this point. Then it becomes about proving herself correct. About putting the past behind her. That, if she didn't kill this fool and prove that his way was wrong then she'll have lost any justification for her existence and acquisition of power. She had to join up with Salem. It was the only way to become powerful, strong and respected. She had no other choice. But in addition to these thoughts there was also a new emotion bubbling to the surface whenever she interacted with Jaune. Respect. Admiration. For the person who was just like her. Showing stout determination in the face of those who deemed him weak. Driven to prove them wrong. Absolutely dedicated towards achieving his ambition. These such traits would lead to her sparing his life on occasion and additionally, she finds herself slowly yet surely looking forward to their encounters. She remembers his name now. How could she forget? Jaune Arc? The name practically rolled off the tongue. Now whenever he appears before her stronger than he was before she can't help but grin. Eager to attack him. See how far he's come. At this point she's nearly forgotten her hatred towards Ruby. She was enjoying watching Jaune improve himself simultaneously proving wrong all those who doubted him. Even her.
Similarly, we see that Jaune slowly starts to understand Cinder over the course of their encounters, whereas in their first official meeting he couldn't comprehend her actions at all. He starts to relate to her intense drive to be something greater. Bits of information lead to him coming to the conclusion that at one point she was someone like him, weak and helpless. However she'd actually achieved her goal. Coming from absolutely nothing to someone so powerful. Which gave him hope of him doing the same. But her path has made it clear she didn't have any of the heartfelt support that he did. Her having only the monstrous Salem to turn to. Jaune against his better judgment begins to feel sorry for the known as Cinder Fall. Yet the same time he'd also begrudgingly come to respect her and all that she'd overcome. But he was confused. Why did she desire further power? Did she not see how strong she already was? Then it dawns on him. She had already overcome so much yet she hasn't overcome herself. She was still so lost in her own anger that it has blinded her to the realization that she had already achieved her goal. So Seeing her as the monster he could have become, Jaune makes the decision to let go of his hate for Cinder. Lest it turn him into a monster as well. Thus no longer feeling hatred for the woman he so consistently opposes he begins seeking answers. To learn why she is the way she is. After, learning of her past her understands what he must do. Spending all his time with Ruby had taught him that being a Hero was about more that just rushing in and slaying some monster, it was also about lending a hand to those in need. Even if they didn't deserve it.
[Fight Details: Removed]
So their fight concludes with Jaune completely besting Cinder. Jaune's final blow kills the parasite Grimm within her. Cinder dies only for a moment before Jaune's powers restores her again, but in that brief moment she remembers Ruby and how pointless her hatred towards her was. How petty she was back then. This brief moment of repentance causes the maiden powers to be sent to Ruby. With this victory, Jaune crushes her ideals and sets her back to Zero. Destroying her Grimm parts and using his semblance to restore her limbs and heal her scars. She is completely human once more. Giving her a chance to start over.
These two characters on every conceivable level whether it's their personalities, characterization or themes simply make for the better conflict. It works because Jaune's existence attacks her beliefs about herself and her motivations for being on the path she's on. Cinder's existence provides Jaune with motivation while attacking his weaknesses as a character while pushing him to be better.
- I think Jaune saving Cinder is perfectly valid a conclusion. Seeing as the narrative seems to be gearing towards saving Salem rather than trying to destroy her. I think this is a good way to build on that idea. Remember they won't see victory entirely through strength but rather by understanding and then saving Salem. Since killing her doesn't solve the problem. Doing it with Cinder first is just a great way for the story to allude to that idea a little further. So Jaune helping to rid Cinder of her hatred and desire for destruction and then giving her the option to choose her own path from here on out is the best way to go imo. While some would argue that they just want to see her die, that might be emotionally satisfying in the moment but Jaune saving her is the better conclusion because it is essentially one big middle finger to her entire way of life.
-Some context into their conversation during the fight that causes Cinder to change her mind are missed but I'm hoping I painted a well enough picture for you guys to imagine it yourselves. Theres also the potential for this to go in a romantic direction if they wanted. Maybe have Cinder recognize her feelings, realizing that the Prince Charming she had dreamed would one day save her(remember she's Cinderella) had arrived but ultimately coming to the conclusion that in the end it was far too late as because he would be in love with someone else. Also, how ironic would it be for Cinder one of the main villains would be the first to see Jaune Arc as a Hero? Thats another reason this works. Once again, theres so much story you can pull out of this. As I've said before it makes little sense for Ruby to have a stake in Jaune's conflict with Cinder. That'd be like having Ruby be the one to kill Adam instead of Yang & Blake i.e. the characters who he had been directly antagonizing. Ruby vs Cinder might have had some credibility if they had any noteworthy interaction at all but sadly that was not the case. Ruby has Salem to worry about. She shouldn't be focused on Cinder.
-I know some people might take issue with Jaune's powers being able to restore limbs but Semblances grow over time. I wouldn't be surprised if near the end of the series his powers reached a point where they were capable of such a feat. His power of Amplification is one with vast potential that goes beyond healing and other boosting semblances and it's something I'd like to talk about at a later date.
-Another thing people might take issue with is Jaune surpassing a maiden but it's entirely appropriate imo. It was never really stated to be impossible just rather difficult since it's a fraction of Ozma's original power. Moreover Magic is the second Power System introduced in the series. When it comes to battle series you should not have one Power System that is inherently superior to another. Such an escalation leads to poorly handled Power Creep. Therefore Magic should not be inherently superior to Aura and any difference in strength/ability should be entirely dependent on the user's own hard work.
-If theres one thing Jaune should be doing it's constantly training. That kind of all day, every day, work all day, sleep all night Roronoa Zoro/Rock Lee training routine. It works as a great way to keep him off-screen since most people hate Jaune and would rather not see him at all. In addition to that it's a great way to ensure that despite no longer being on-screen as often as everyone else we have assurance that he's always progressing and doing something even if we can't see him anymore. So whenever people ask why Jaune isn't part of the story it should be because he's doing laps around the city. Or he's carrying boulders up a mountain. Or sparring with the local swordsmen. Something.
-One more thing that I neglected to mention earlier that leans into the idea of Jaune & Cinder being used to represent the greater conflict between Ozpin & Salem(and I mean strictly thematically not romantically) is that one of Jaune's themes is that he represents The Sun. Jaune's first name meaning yellow in French and the etymology of the name "Arc" not only has "Holy" connotations but is also a reference to the Sun. Jaune Arc essentially means Yellow Sun. The reason this is significant is because the Sun in ancient times was worshiped as the "Life Giver". Which is literally Jaune's Semblance. So Jaune is the Yellow Sun that Gives Life and Cinder is the burning flame that reduces all things to Ash. One representing Life and the other representing Death and Destruction. Much like the God of Light & Darkness but more importantly like Ozpin & Salem as it makes for a great way to symbolize the Cycle of Life, Death & Rebirth. With this in mind if my scenario plays out, the scene where Jaune saves Cinder can be read as: "a wild flame reduces all life around it to Cinders but through the light of the Sun that life is reborn from the ashes anew". Does that mean Cinder would get a new Semblance as a way to symbolize how she's been reborn? I dunno but it would be pretty cool if she did.