I don't really believe it'd be possible. There isn't really any such thing as a "bad guy", just an entity that opposes yours. Even the "bad guys" think that their side is the "good guys".
If any type of game let you know that you were fighting FOR the bad guys, any person in a real situation might say, "Hey. I don't think this is right," and switch sides. For example, the Czech wants to wipe out every single bunny for no apparent reason, other than getting everyone's knickers in a knot. Actually, some people may do that just for the fun of it. Bad example.
The point is, an inner feeling of well doing would most likely set off some kind of bell, likely making the player not want to participate.