Hammer because his pre-sellout stuff was great. "Turn This Mutha Out"..it's still awesome. After that he became embarrassing. I don't know which was worse, his Adams Family rap or him then trying to go "gangsta" in the mid 90s.
Vanilla Ice, where to start. I'm pretty sure he didn't write Ice Ice Baby, on top of that he lied about where he was from. He also made the worst movie ever "Cool As Ice" and to top it off his second biggest hit was "Ninja Rap" from TMNT 2. He too tried to go "gangsta" in the mid 90s and his results were even worse than Hammer's.