10 Most Evil X-Men Villains
8. Shadow King
The Shadow King is one of the X-Men's oldest foes and technically responsible for the formation of the team.
As the telepath Amahl Farouk, the Shadow King became a crime lord in Egypt and encountered a young Charles Xavier after one of his pickpockets robbed him (that pickpocket being Ororo Munroe). Farouk tried and failed to convince the future Professor X to join him and so the two fought. It was a viscous battle fought on the astral plane (an entire world built by people's minds) and Xavier could only win by killing his opponent with a bolt of psychic energy. It was this incident which inspired Xavier to form his own team to fight against evil mutants.
However, it turned out that the Shadow King was more than just Amahl Farouk. The real Shadow King was a psychic entity who lived on the astral plane and had merged with Farouk when he first discovered his powers. The Shadow King was able to keep returning to plague the X-Men, possessing a new host body each time.
It's a terrifying thought, that at any point your mind could be taken over by the Shadow King and you'd be forced to do his bidding, a prisoner in your own body.
Also he really likes to make his bodies eat and we all know it's so much easier to put on weight than lose it. What a nightmare.