Now I'm Pissed Again.
I just found this image and forgot I even posted it. After I had beaten Pillar of Autumn and Lone Wolf on Legendary by myself, and the achievement didn't pop. I went to the mission select screen and this is what I saw: (Note this was way back when I didn't have the "i" in Sir in my Gamertag.
Long story short I had to redo every mission except the last all over again. Goddamn Reach, you have screwed me over time and time again but I keep coming back. I'm like the abused spouse who keeps coming back because he says he's sorry and he'd never hurt me again.