I have one friend like that. He started out as just a little crazier then the rest of us, then he slowly got worse and worse. He frequently drives drunk(He says he's a better driver drunk, which actually wouldn't be hard, considering how he drives while sober), and...well, he just became a DICK. For example, I mentioned that one of our friend's parents were out of town for a weekend (I brought it up late Sunday) and he was actually OFFENDED that that friend hadn't thrown a house party. Like it was his DUTY or something.
But I really stopped respecting him when he started cheating on his girlfriend CONSTANTLY. Eventually, they got to the point where they hated each other, but he somehow convinced her not to dump him, even though he didn't give two shits about her. Why? Because he liked cheating on her. He even asked me to lie to her about his cheating, and basically called me a bad friend for not doing it.
Proud to say I haven't seen him in about a month.