If he's a good enough friend, you might just tell him point blank: "You always play a chaotic evil character that backstabs his friends. It's no fun for anybody else because they always have to worry about what you're going to do to them, and it distracts from the larger story which should be about the team solving problems, not fighting against each other."
Hard to say things like that in person, but maybe he simply hasn't thought through how much impact his style of play has on everybody else. Maybe he'll clue in. But if it turns out he simply doesn't care, then...so long and don't let the door hit ya on the way out.