Not an eligible player, but Demond Williams, formerly the quarterback (and a potential star, at that) of the Washington Huskies, is about as selfish and scummy as it gets. Signs with Washington for a lot of money, then posts an Instagram post - while a deceased female student-athlete that everyone around the university adored is having her memorial service done with most of the team in attendance - saying that he's leaving with a do-not-contact designation about a week later.
Washington's trying to fight it with the NCAA, but honestly? I'd just let him go, look at other options when he clearly is trying to get as much money as he can. And when he comes out into the draft, I've got him on my Do-Not-Draft list. If you're scummy and selfish enough to try to upstage a damned memorial for a student-athlete that most of your football team is there mourning her, you're scummy and selfish enough to do anything bad.