I know that these are technically four people, but both come from games that in my opinion rely heavily on two man co-operation to be effective. Therefore I consider both two man teams to be the equivalent of one goodie and one baddie.
I would love to see a deathmatch between Marcus and Dom from Gears Of War vs Rios and Salem From Army Of Two. I consider Rios and Salem to be the bad guys on the grounds that I picked all the evil choices in 40th day. Which, if you've ever played 40th day makes them the biggest pair of total assholes I can think of.
(SPOILER ALERT)Anybody who betrays an ally for money, kills and innocent guard for free guns, wipes out a species of rare tiger for a gun part, gets a little kid shot for a 50.cal and risks setting of a nuke so they don't have to shoot their mate, truly deserves a swift and brutal chainsaw intrusion where the sun don't shine.