One thing that is bugging me is how in a twist everyone's panties - including Ozma - are over the fact that Salem can't be "destroyed". While maybe I could see it getting at Ruby, Yang and Weiss - Blake (an experienced guerrilla fighter and saboteur), Qrow (and experienced Huntsmen and Hunter of Hunters) should've been able to realize that "stop" is NOT the same thing as destroy.
Hell, Raven, smart as she is, should've been able to think this one through.
Ozma, with his centuries of experience, should've been able to come up with this one.
You don't need to kill an enemy to neutralize them - just put them in such a state that they no longer pose a (significant) threat to you or your goals.
Salem can and *does* suffer injury, damage. She can be hurt, even to the point where her entire body is destroyed, and then has her "Can't die" clause take effect and resurrect her. It's likely why she doesn't do anything herself, because she still feels pain and can be stopped (temporarily) by having her body destroyed - otherwise there'd be no point in wasting time with minions when she could just casually stroll down the streets of Remnant pimp slapping all of Humanity and Fanus to death at her leisure, unable to be stopped.
But thanks to Salem herself, Cinder and the God of Destruction we know magic and a person's powers can forcibly be taken away from them. So strip Salem of her magic and command of the Grimm and suddenly she is no longer a massive threat and can safely be ignored.
Let's say that isn't possible though - then there is another option. For those of you into comics, you might've read World War Hulk. In it Hulk is attempting to take over the Earth and must fight Earth's various heroes, including Wolverine and Laura/X-23. Both Wolverine and Laura/X-23 can regenerate to the point where they're effectively immortal and indestructible (from a single cell) and are strong enough to legitimately pose a threat to the Hulk.
Knowing this, Hulk comes up with a rather simple solution;
Have you ever seen a boxer whose taken a few too many blows to the head? Wobbly, trouble with words, bad coordination, not all there?
Hulk simply punches X-23 and Wolverine in the face until they're vegetables. They're not dead, there is nothing to regenerate - their brains are just scrambled eggs and they're effectively harmless.
Apply a generous helping of blunt force trauma to Salem's head over and over and over until she's a drooling mess - don't smash her head and kill her - and let her own "strength" become her downfall. She can't come back from something that isn't going to kill her. She's not dead - she's just, uh, special needs now and effectively rendered harmless. Even if she starts to recover it's not like it's hard to find a bloke with a hammer or someone who punches hard to reapply the treatment.
I mean, it might be a touch morbid and brutal, but Salem is murdering thousands of people and sending hellbeasts to torment them so, you know.
I feel like this is just another case of characters taking "Can't be destroyed" as the end-all-be-all rather than the invitation to get creative that it is.