Fenrir Greyback

"Fenrir Greyback is, perhaps, the most savage werewolf alive today. He regards it as his mission in life to bite and to conta­minate as many people as possible; he wants to create enough were­wolves to overcome the wizards. Voldemort has promised him prey in return for his services. Greyback specializes in children... Bite them young, he says, and raise them away from their parents, raise them to hate normal wizards. Voldemort has threatened to unleash him upon people's sons and daughters; it is a threat that usually produces good results."

Lupin paused and then said, "It was Greyback who bit me."

-- J.K.Rowling - Harry Potter and the Half-Blood Prince