Respected artists who were actually terrible people

It's common knowledge that you don't need a beautiful soul to create beautiful art. Look at any number of famous painters, musicians, or writers, and it's clear that a beautiful soul is a requirement that ranks way below being a higher-functioning alcoholic in the creativity stakes.
But while you're probably aware that not all artists are paragons of virtue, you're likely less aware of just what total waste-expelling orifices some of them are. There are artists out there whose names you can recall with greater ease than you can recall your own mother's birthday, towering geniuses in the worlds of painting, music or design who are so unlovely that spending time with them would be the psychological equivalent of hurling yourself into a waste disposal unit. Think great art can't be made by people who are total art-holes? This pantheon of pimps, murderers, bullies, and rip-off merchants begs to differ.