Shima from Ao No Exorcist- That is one person ANYONE would be hard-pressed not to hate.
Eyebrows, also from ANE- she is a vain, cruel, useless bi*ch...
Every girl from Code Geass, except maybe C2, cuz she's a bit, only a bit, more practical than the rest. Though she is stupid, and not a few times either. But the worst from CG is Euphemia. She is sooo.... AARRRGH!! She grates on my nerves!!