Rick
Rick was a player, yes, but he really didn't do anything bad to Gary. Gary had his chance and never made his move. Rick treated Karen like a dick, but Gary acted like a baby because Rick won the girl. Big deal! I've been on both sides of that situation and me and my friends got a little jealous, but remained friends. I think Gary overreated against Rick.
If anyone should be mad, it should be Rick. Gary (and David) pressured him into banging that whore thus giving him crabs. Rick didn't really want to go along but they ostrisized him into it. Did Rick get mad? Not really. He just moved on with his life and didn't act like a crybaby like Gary did.