Magneto

Perhaps one of the more powerful villains in Marvel and comic book lore, however what I believe makes him such a scary villain is the fact that he thinks his motives are right. His true identity as Erik Lehnsherr has a deep backstory, traveling back to the Holocaust where he was separated from his parents who both eventually died. Since then, Erik discovered his mutant powers which allow him to control magnetic fields and manipulate metal. He leads a resistance against the US Government seeking civil rights for mutants and more. Magneto firmly believes that mutants are the higher power and humans have no place on earth, this is what makes him so horrifying. Along with nice character development and interesting motives, performances by Sir Ian McKellen(Lord of the Rings) and Michael Fassbender(Shame) in the X-Men Franchise. Ranked #1 best comic book villain by IGN.com in 2009, Magneto remains a force in cinema. Often compared to Malcolm X, Erik Lahnsherr is a notable character in comic book lore and will remain so through film as he is expected to star in X-Men: Apocalypse in 2016. 

9/10