Christina Aguilera vs Kelly Osbourne

The war between these singers turned so nasty that they once ended up in fisticuffs. 'She is the nastiest person I have ever seen,' said Christina of Ms Osbourne. 'She is so bitter and twisted about life.' Kelly lashed out in retaliation, calling Xtina 'one of the most disgusting human beings in the entire world,' and adding: 'I've seen drag queens who look better. She has a bad mouth on her, but she's all talk.'
Kelly O

They reportedly came to blows at a club when Christina ran at Kelly, got her in a headlock and told her in no uncertain terms to say things to her face in person. The alleged catfight ended when they both stormed off.