Lord Voldemort (played by Ralph Fiennes)
Lord Voldemort was born Tom Riddle, but those who fear him most call him "You-Know-Who" or "He-Who-Must-Not-Be-Named."
This Dark Lord grew up unloved and eventually killed his Muggle family before starting a bloody war for pure-blood supremacy, though he is a half-blood (half-Muggle, half-wizard) himself. His physical shape has changed over the years, and he now appears as a skeletal figure with a snake-like nose.
Voldemort is embarrassed when young Harry Potter evades his grasp, and it becomes his lifelong goal to take down Harry and anyone who stands in his path.
Photo: Warner Bros.