Play in the dark with head phones on. Human campaign > Alien campaign. Best guns: Zapper for close-range, sniper for long-range (but you only get one shot at a time). Strongest: rpg. Get mm pistol whip and indecisive on easy quickmatches. Don't your team when they get infected. Up if it helped at all please. Ignore if it didn't.
So, Level 21. I FINALLY get past the awful gray avalanche that you have to do. Then, I see the end of the level below me. I fall... AND MISS> *resumes to pulling hair out*.