9. Cassandra Nova (Julianne Moore)
Cassandra Nova is a fairly high-concept villain, even by comic book standards. She began life as a Mummudrai, a parasite made up of emotional energy that was born without a body on the astral plane. She came into physical being upon forming a telepathic bond with Charles Xavier, when he was still an infant in his mothers womb. And so Cassandra Nova was born into a physical form. She became the distorted and dark ideological mirror of Professor X, preferring destruction and genocide to peace and goodwill. On one notable villainous tirade, she massacred 16 million mutants with an army of Sentinels. Cassandra Nova could be the darkest and deadliest mutant to grace an X-Men movie, if Fox ever have the guts to include her. Itd certainly be interesting for a villain to have so close personal bond to Charles, but be so utterly unlike him. Even Magneto draws the line at killing mutants, after all. Julianne Moore would be perfect casting. Shes played evil in The Hunger Games franchise and delivered a note-perfect English accent in End Of The Affair. All shed have to do is combine these skills and stick a bald-cap to become an amazing cinematic Cassandra Nova.