How do you deal with this guy? I've run through three games (two death match and one story mode) and he seems over-powered. Maybe it's my dice rolling luck but I haven't been able to kill him (but Karl has no problem killing the Union side). Is the best strategy simply to avoid him?

Karl is hard one to deal with. I recommend using some smoke granades to cancel his good shooting spots it's just the first step, but it should help.

thatl help, also it depends on how he is played, defensivly he can be a monster, but in things like ctf, he isnt allways as good as he needs to get into the thick of it, ramirez has cut him down many times for me

i've found that Ramirez and hound dog are very effective against him. Though with his combat pack he is a monster from range and close combat. Grenades are very effective as well, those auto wounds do wonders.