6. Amy Burley (True Blood)
Boasts of an organic vegan lifestyle didn't make Jason Stackhouse's (Ryan Kwanten) tree-hugging ex any less of a blood-thirsty psychopath. With an itch that could only be scratched by vampire blood (a powerful upper known simply as "V" in the twisted world of Charlaine Harris-authored fantasy), Amy Burley (sexy Lizzy Caplan) resorted to kidnapping and imprisoning an innocent vampire so that she could have her own fresh supply whenever she liked.
Helpfully suggesting that perhaps a sense of Stockholm syndrome would kick in, to appease her boyfriend's stress over the situation, Burley begins to feign niceness with her captive. It doesn't last long. Once her man takes a stand for their deceased new housemate, she loses her shit and stabs the vamp in the heart, resulting in a spewing of blood and guts all over Stackhouse's basement.