7. Proteus (Doug Jones)
Proteus (real name: Kevin) is the son of Moira McTaggert (played by Rose Byrne in X-Men: First Class and X-Men: Apocalypse), who was born as the result of a forced marriage and a rape. When his mutant genes manifested, Kevin developed an unquenchable desire to consume energy that he couldnt control. Proteus regularly harvested human lives in order to survive. He was capable of transferring his essence between bodies and possessing people, which made him a very difficult adversary for the X-Men to track down or defeat. Most superpowered attacks dont affect him, either. This could make an interesting topic for a movie, which could see Proteus assuming the identities of powerful mutants as part of a deadly rampage of consumption. Hed certainly be unlike the X-Men movies audiences have seen before. Doug Jones is the man to go to if Fox are looking to cast a being of pure energy. Hes used to disappearing into roles (such as the Silver Surfer, the Pale Man and Abe Sapien from the Hellboy films). Proteus would allow Jones to portray wild, unhinged evil, which could be a thrilling sight to behold.