I loved reading this thread so much; I want to add my list. I am restricting myself to the stuff I have listened to, the list could be longer although.
Katy Perry: Just for that I kissed a girl song ugh.
Britney Spears: She is as lousy singer as a human being
Rhianna: I’ve have listened to her albums and they are awful. How she got so big is an utter mystery to me.
Eminem (A lot of his fans are dumb, really they are)
50 Cent
Hillsong: That stuff, along with modern Christian music is like having your head drilled in.
ABBA
Westlife
Creed
Nickelback