Red Skull
During the 2014 "AXIS" storyline, Magneto enters the island of Genosha to find that it has turned into a concentration camp for mutants. He frees two mutant girls who tell him that Red Skull is responsible and possesses Professor X's brain. Magneto attacks Red Skull, but is quickly stopped by his S-Men. Magneto is captured and mind-tortured by Red Skull. He is given visions of those closest to him suffering while being unable to do anything to stop it. After being freed by Scarlet Witch, Rogue, and Havok, he bites down on a vial beneath his skin of Mutant Growth Hormone, giving himself enough power to fight. When Havok, Rogue, and Scarlet Witch want to leave the island and alert the rest of the Avengers and X-Men of what Red Skull is doing, Magneto says he's going to stay and fight. Before they can do anything, Red Skull appears. Red Skull now has the group mind-controlled. He plans on using Scarlet Witch's power to shape reality in his image. He tells Magneto to bow if he wants his daughter to remain alive, but Magneto performs a sneak attack enough to break Red Skull's control over the others. In a fit of rage over finding mutants being used for freak medical experiments, Magneto kills the entire S-Men team. Magneto then attacks Red Skull, all while Red Skull tells Magneto that Professor X's greatest fear was him leading the X-Men. Magneto kills Red Skull while the others look on in horror. Magneto believes everything is over only for Red Skull to reappear as a giant called Red Onslaught.