Magneto should be a

What Claremont intended was the best - He was a traumatized individual, hunted by tragic events whenever he went, to a point where it drove him mad, through madness (that combined with abuse of powers) he became a mad villain, after recovering his sanity, started to see his ways of achieving the goal were deadly and ineffective, started to recover but still maintained the edge for violence. So you could say it's an antihero.

From there he wasn't supposed to be a villain again, but cyclic nature of comics ruined this organic and magnificent arc.