The mutant known by many names, foremost among them "Magneto," is the most layered super-villain in the Marvel universe, if not superhero comics. Magneto witnessed how cruel mankind can be to those that are different during a childhood spent in Auschwitz, so now he fights to ensure mutants will never face the persecution he did during the Holocaust.
This means Magneto has firm ideological divides with his frenemy, mutant integrationist Charles Xavier. Still, his fundamental nobility and care for Mutant-kind mean that Magneto can just as easily be an ally to the X-Men as an enemy. Here are five stories where he was his most heroic, and five where he was most evil.
10 NOBLE: "I, Magneto..." (Uncanny X-Men #150 By Chris Claremont & Dave Cockrum)
This double-sized issue was a turning point for the Master of Magnetism's character. Chris Claremont wanted to flesh out Magneto's character to reveal the "who, what, where, when, and most especially the why of his life and his origin.” Claremont wound up drawing on his own Jewish heritage and concocted Magneto's Holocaust survivor backstory; this wrinkle to his history and motivations instantly made Magneto one of Marvel's deepest villains.
This new backstory, and a less overtly evil persona to go along with it, debuted in X-Men #150. When Cyclops reveals the demise of his beloved Jean Grey, Magneto's offer of sympathy is rebuked; Magneto in turn angrily reveals the massacre of his own family to Scott. Later, believing himself to have accidentally killed Kitty Pryde, Magneto's mind floods with memories of both his experiences at Auschwitz and the later death of his daughter Anya. Crippled by regret at what he's become, Magneto surrenders when Storm confronts him.
9 EVIL: The Silver Age
Claremont certainly had his work cut out for him; though the results were a tremendous success, Stan Lee & Jack Kirby's original X-Men comics hadn't left him much to work with on Magneto. First appearing in the team's eponymous debut issue, Magneto is one of the few villains from the earliest days of X-Men who's endured, by sheer frequency of appearance if nothing else. However, the Lee-Kirby Magneto is a pale shadow of the character Claremont would develop, concerned only with conquest and lacking either empathy for his fellow mutants or much reasoning for his actions.
8 NOBLE: "God Loves, Man Kills"
If "I, Magneto..." showed that the villain could become a more noble character, "God Loves, Man Kills" brought that idea to fruition. In the story's opening moments, Magneto comes across the aftermath of a hate-crime, two mutant children killed and left up as an example by the bigoted "Purifiers." After mourning them, the sincerity of his sorrow clear even without the sound to portray it, Magneto goes to the X-Men. Not as an enemy but, for the first time, as an ally. Together, he helps the team rescue a captive Professor X from the Purifiers and stop the plans of their leader, William Stryker. Still, his ideological differences with the team mean the alliance is over by the story's end.
7 EVIL: "X2: X-Men United"
X2 is a loose adaptation of "God Loves, Man Kills." The film version of Magneto (alongside his acolyte Mystique) likewise joins the X-Men to stop Stryker's plan, using Professor X's telepathy to wipe out all of Mutant-kind.
Unlike his comic counterpart, however, Magneto betrays the team in the story's third act; he decides not to stop Stryker's plan, but hijack and invert it, so that Xavier's telepathy will kill all humans instead. He thus callously leaves his old friend Charles trapped, willing to let him die if it means mutants inherit the Earth.
6 NOBLE: New Mutants
After fighting alongside the heroes of the Marvel universe in Secret Wars then standing trial for his crimes in Uncanny X-Men #200 by Chris Claremont & John Romita, Magneto finally reconciles with Charles. Xavier, on the brink of death, is forced to travel to Shi'ar space alongside his paramour Empress Lilandra so that he can be healed. He asks Magneto to take over the school in his absence, and despite doubt about his worthiness, Magneto accepts. Thus Magneto officially goes from the X-Men's enemy to ally; under the assumed identity of Xavier's cousin Michael, he becomes headmaster of the New Mutants from issues #35-75 of their eponymous series.
5 EVIL: "Fatal Attractions"
Superhero comics are inevitably torn between storytelling consistency and brand consistency. Thus, Magneto's redemption was only temporary; by 1993's "Fatal Attractions," he had returned to his villainous roots. This story includes an infamous scene where Magneto uses his powers to horrifying effect; always able to best Wolverine due to the X-Man's adamantium-coated skeleton, Magneto outright rips the adamantium from Wolverine's body. The damage is so severe that even Logan's healing factor just barely saves him, while Xavier is so enraged that he wipes Magneto's mind and leaves him comatose.
4 NOBLE: X-Men (1992)
The 1992 animated X-Men remains the biggest success the team has found on the small-screen; it also contains one of the most outright heroic versions of Magneto. Voiced by the late David Hemblen, Magneto is only villainous in his two-part debut episode; every subsequent appearance has him acting as an ally to the X-Men, usually against a greater evil. Some particularly notable instances include the duration of Season 2, where he and Xavier, deprived of their powers, wander through the Savage Land together, or the four-part "Beyond Good & Evil" where he helps the X-Men overcome Apocalypse. In the series finale, "Graduation Day," he even sacrifices his dreams of conquest in favor of helping to save Xavier's life.
3 EVIL: "Planet X" (New X-Men #146-150 By Grant Morrison & Phil Jimenez)
Magneto seemingly perishes in the genocide of the Genosha early on in Grant Morrison's New X-Men run. However, in the series' sixth story arc, "Planet X," it's revealed Xorn, a mutant introduced during the run, is actually Magneto in disguise; he'd infiltrated the X-Men with the intent of destroying them.
In moves that would make his Silver Age self blush, Magneto re-cripples Xavier (who'd been healed of his paralysis in an earlier story), subjugates New York City, and even begins sending humans to gas chambers like the ones at Auschwitz. Reader backlash prompted a retcon that Xorn had merely been impersonating Magneto, but in the text of "Planet X" itself, there's no indication of this.
2 NOBLE: "The Age Of Apocalypse"
The "Age Of Apocalypse" charts a different course in life for Magneto. Xavier's son David traveled back in time with the intention of killing Magneto and retroactively sparing his father a boatload of heartache. The plan backfired when the young Xavier was killed instead. This lead to a timeline where Apocalypse had enslaved Earth, with only the X-Men to oppose him. These X-Men, however, were founded and led by Magneto; after Xavier's murder, Magneto vowed to continue his friend's work in bringing humanity and mutants together. Thus, he founded the X-Men, naming them in memory of Charles.
1 EVIL: "Ultimatum"
The Magneto of Ultimate Marvel is a far viler character than his mainstream counterpart. His goal is not the survival of mutants, but the subjugation of humanity - a most important distinction. He also lacks his mainstream counterpart's childhood experiences; he's motivated by narcissism, not trauma. His evil comes to a head in "Ultimatum" - using his powers to wield Thor's weather-controlling hammer Mjolnir, Magneto drowns New York City with a tidal wave. This kills millions, including many superheroes. Magneto takes things further by personally killing Xavier then attempting to disrupt Earth's magnetic field, but his evil is ultimately ended once and for all by Cyclops.