Aside from dictators (who are by definition very, very shitty people, but almost always have an art career for some reason), assuming actors don’t count as artists, I’d have to say the only example I can think of is Butch Hartman, not shitty because of his character but because he’s like the other JK Rowling.
To answer the second question, literally all the e-artists I’ve ever met, though art is relative enough I don’t feel like art can have a “negative” value. I trust they will never see this.