Bieber (or those he's doing damage control and cleaning up his image), Chris Brown (I don't think he'll ever recover which is a shame considering how talented he is) and Mariah Carey.
Also Janet if you count the Superbowl thing. But that wasn't an attitude/behaviour thing or lackluster music. That was due to a controversy.
She had very good songs. But she could not perform live. And I think, with er drinking problems, she died. So I don't think there's something more to kill her career.