I’ll get to the point: What is that supposed to mean? Finish a level in a single sitting, or the whole game, or solo (no co-op)?
It doesn’t say
I think it means you can’t just revert to the previous checkpoint and expect to get the achievement.
Otherwise, it’d be really easy to kill 4 wraiths with the scorpion. Just kill one, revert to previous, and get another one.
I don’t know if that means you can’t die in the process. Just keep trying, I guess.
Nah, that just means you have to do those parts without reverting to last checkpoints or dying. There’s some missions where you can die as many times before reaching those points, but if you die in the middle of doing whatever, you won’t get the achievement. Like destroying the 4 Wraiths using a tank on Assault on the Control Room level. If you die, like say after getting 1, 2, or 3 Wraiths down, then you have to do that whole mission again and go back to that point. Just as long you destroy those Wraiths in a single play, then you’ll most likely get the achievement. So if you die before you get to that point, don’t worry because it doesn’t count against the chance of getting the achievement, you just have to worry about not dying while destroying them. I hope that helps.