Who else? The first villain the X-Men ever faced and still by far the best (even if he's more of a good guy than bad guy nowadays), Magneto is one of the Marvel Universe's most iconic characters and he's committed some truly horrific acts over the years. While there have been some bumps in the road - it's probably best to act like that whole Xorn thing never happened - those are easily forgiven when looking back at his legacy. That obviously includes fathering Quicksilver and the Scarlet Witch and making them part of his Brotherhood of Evil Mutants, tearing the Adamantium from Wolverine's skeleton, and in the Ultimate Universe, leaving crippling Charles Xavier after impaling him through the back with a metal spike. Even now he's on the X-Men's side, Magneto's villainous ways still shine through, and he'll no doubt go back to being bad soon enough.
