Christina Aguilera - I used to adore her and her music, especially during the Stripped era. But then Back To Basics and Keeps Gettin Better both sucked and I don't think I will like her new album either going by what I've read. I also hate her live singing so much.
Maroon 5 - Used to like their music but now I find it so bland and Adam Levine's voice very irritating.
Avril Lavigne - I thought she was brilliant during her first two eras and then since Girlfriend she has gone downhill and she has a horrible personality.
Beverley Knight - I was never a huge fan but I liked a few of her tracks and her voice. Now listening back, I find her voice very harsh to listen to and her songs don't do anything for me. I also find her personality very annoying in recent interviews.
During high school I went through a phase of liking bands like Fall Out Boy, Panic! At The Disco, All American Rejects etc and now can't listen to their music at all.