Debra from Dexter.
She's coarse, foul mouthed, unattractive, and clueless. She tries hard to be one of the guys and in the end she's just horrible. In a show that I ended up hating, I hated this character the most.
Jay from The Inbetweeners.
Ugh, I want to punch this character's face every time I see it. And when he opens his mouth to spew his bullshit, I want to drop a truck on him. I've been around know it all bullshit artist guys like him all my life, until recently, and I hated each one of them. He's always spewing sexist bullshit, lies, and tall tales, and then he takes no responsibility for any of it, so in other words, he's a modern conservative.
Jackie from Nurse Jackie.
No redeeming qualities whatsoever. She's an addict who revels in her addiction and she doesn't care who she hurts in order to stay high. By the end of the series I stopped rooting for her to stay clean and began rooting for her to overdose and die so she wouldn't be able to hurt anyone else.