Jon Bon Jovi
How 'bout the worst?
That guy from "System of a Down" sounds like a sick walrus being beat with at billy club. It's a shame too because their music is very good. But when the "singing" starts I gotta change the channel. It's intolerable.
I like Serj Tankian. He doesn't sound like anyone else.
Singing is all about hitting the right notes, which is what he does. You obviously just don't like his singing voice. I guess it is an acquired taste...