N*gger trumps c*nt any day. Both are insults; only one has history, and social implications behind it. Also, use of c*nt is directed at one person specifically, and does not necessarily imply the offending user is a mysogynist. Indeed, plenty of women will call another woman a c*nt with out hesitation. However, one use of the word n*gger, while often directed at one person, tends to imply that the user is making a statement about an entire race (they are certainly letting their opinions on the subject known, being that most who aren't racist shy away from the word). Chris Rock proposes a good argument on the topic (yeah, pretty much what Pryor said--I'm referring to the difference between African Americans and n*ggers), but n*gger does have far more behind it thatn c*nt ever will.
As far as these forums though, I would have to agree that "evolution" or "atheist" are the most offensive words
