Voldemort? He who must not be named? is the arch enemy of Harry Potter and determined to destroy him. Despite being a half blood himself, he is obsessed with pure bloods and wants to subjugate all muggles, and take over the both the muggle and wizarding world. He is described as the most evil wizard for hundreds and hundreds of years and a psychopath devoid of human feelings.  He also has a pathological fear of death. He is not a nice guy!