Reprint of and retroactive backup story to The X-Men #113 - Showdown! (September, 1978).
Somewhere in South America, after the end of the second World War, Nazi soldiers have established a base to evade justice for their war crimes.
Out of the surrounding jungle emerges a lone, unarmed figure whom the guards open fire upon. As bullets bounce off the figure, he raises his hand causing the outer walls of their fortress to crumble. As more soldiers open fire on him from a tank, the man scoffs at their efforts, for he is Magneto, the master of magnetism!
Seeing his objective, Magneto hurls the tank at a high tower and levitates himself inside to confront it's inhabitant: a former German Bannfuhrer, Hans Richter, who Magneto has hunted to bring to trial for his crimes. As the two argue, Magneto is overcome by incredible pain; his powers are still new to him, and part of him worries that his recent endeavors have taxed them too much. Recovering, he tears opens Richter's office safe to reveal his spoils of war and further condemn him before telephoning someone he calls Control to establish that Richter has been caught.
Weeks later, on a beach in Rio de Janeiro, Magneto is reading a newspaper article about his friend Charles Xavier. Though he sees Xavier as too politically idealistic, he respects him as a doctor and is interested to hear that he's opened a school, thinking that perhaps he would have some insight into the pain that he's been having when accessing his powers.
He's joined by his friend Isabelle, a physician with whom he's starting to have an affair, and the two retire to a hotel room. As they embrace, Magneto apologizes that he is still not over his wife. Though she abandoned him, he understands why and is not fully able to move on. Suddenly he again suffers the pain brought on by his powers. He and Isabelle talk about the pain he's been suffering, and she gives him a massage. She starts giving a theory about what could be causing it, but before she can finish it she's cut across the throat from behind by an unseen assailant.
Magneto rises to see the hotel room has filled with assassins lead by the man he'd been reporting to: the mysterious Control. Control informs Magneto that his last mission, capturing Richter, was unsanctioned and as such, he himself must be stopped. Magneto argues that Richter was a Nazi and a war criminal, but Control explains that he's not seeing the big picture, that the Russians are the enemy now, and that Richter was an asset to be used just as mutants are.
Magneto, furious at this abuse of his trust, lashes out, but Control wears a special vest that turns Magneto's power back at him. Magneto, refusing to be killed by a man like Control, blows up the top of the hotel. His men dead and his vest broken, Control cowers below Magneto. Magneto tells him he's had it with humanity and that now he sees his true path: to conquer humanity in the name of the more evolved mutantkind.
"It is I who shall lead my people to the glory they deserve, I, ubermensch, I, Mutant, I, Magneto!"
This is a pretty interesting side of Magneto's story that seems often forgotten. That, even after his terrible childhood in Auschwitz, even after witnessing the death of his child, and being abandoned as a monster by his wife, Magneto is still trying to work within the system to achieve justice. Though he is hunting down Nazi war criminals (as we see him do in the X-Men: First Class film), he's not just killing them, but rather delivering them to face trial for their crimes.
Claremont seems to imply with this story that it's only after trying to work alongside the justice system that Magneto becomes disenchanted by it's corruption, and, blaming that corruption on all of humanity, seeks to supplant it with is own new form of revolutionary government.
It's a small detail in Magneto's story overall, but Claremont must have seen it as especially relevant considering he gave the story (basically) the same title as Magneto's first major turning point from the 1981 story, I, Magneto.