Magnetor

Magnetor (originally named Magneto) was a pre-Marvel comics character featuring in Strange Tales, 1961 - this makes him one of Marvel's earlier supervillains, since the "official" Marvel age is not usually seen to begin until after the release of the first Fantastic Four comic (which sparked the "modern age" of Marvel canon).

Like all characters and events in the "pre-Marvel" comics Magnetor is not canon in the current Marvel universe but is also not completely eliminated from said canon - rather he can be considered "in limbo" until writers or events within the "mainstream" Marvel universe counter his existence one way or the other.

History
Magnetor was originally a large, strong and slow-witted human by the name of Hunk who came to the city seeking employment but was unable to do so as society mocked his strange appearance and mannerisms, he was also manipulated by a con man who tried to use Hunk's strength to get rich by giving him varied jobs, which he ultimately failed due to his strength or poor social skills.

Eventually Hunk gained some employment in a freak show but grew angry at being mocked, attacking a guest and thus once again found himself fired and seeking any way to gain employment.

Ultimately Hunk would find an advertisement on TV for astronauts and applied, going as far as DC itself to enroll, the scientists approved him due to feeling his great strength would be of use in the work and thus Hunk soon found himself on a rocket into space - yet fate once again conspired against him and his rocket was bombarded with cosmic radiation, forcing him to return to Earth.

Awakening once more on Earth and finding that the radiation had mutated him Magnetor went on a rampage, capable of controlling magnetic forces and combined with his already enhanced strength and 8-ft tall physique he became a dangerous villain seeking revenge on the world.

However his rampage came to an end when his powers faded and he found himself a "normal" human once more, fearful of retribution he allied with the con man who had tried to manipulate him before and gained access to a second rocket which left Earth in search of other worlds, with Hunk finally crying in relief as he began his cosmic voyage to find a world that would not shun or mock him.

Trivia

 * the radiation that mutated Hunk, while not named as such, is very likely the same radiation that would mutate the Fantastic Four and spark the "modern era" of Marvel comics.
 * the idea of scientists allowing random civilians to go into space with little to no formal training is not possible by our world's standards but was a very common plot device in early sci-fi and comics (which were generally less concerned with themes of "realism" than they are today).
 * while Hunk is described as an ordinary human prior to his exposure to radiation he was 8ft tall and capable of lifting cars even before said mutation, this suggests Hunk may of been an early example of a mutant.