Pepcé her personality is what me a hater. Sure her bad music helped, but tons of artists release awful music, she is not alone in that.
B'Day was really the pits though. Déjà Vu in particular, one of the worst songs of all time. She had already pissed me off so much during the DIL era by releasing the two most abominable songs as singles (Baby Boy and Naughty Girl) and DV sealed the deal musically.
But her despicable personality and the way her fans praise it is really what keeps the vitriol going.
What personality though? She is very fake and contrived during interviews and things but for the most part she's just boring.
Out of Beyonce, Gaga and Christina who do they hate the most?
They all seem to like Madonna, don't bring up P!nk, and indifferent towards Rihanna.
It'd have to be Eve when she said Britney didn't sing the vocals on S&S. The Army went IN on her. They also HATE John Legend because he shaded her once. Same with Bobby Brown when he shaded Brit's My Prerogative cover. That's what I've seen based off of my own personal experience.
EDIT: And Adrienne Bailor or whoever the hell from the Cheetah Girls when she said Britney can't hold a proper conversation. They were FUMING. I cackled.