Source: dccomics.com

9. Lex Luthor

(Superman, DC Comics)

It's always the most evil villains who make the best reformed heroes. And Lex Luthor is no exception.

During the events of Forever Evil, the Crime Syndicate took over the world, trapping all three Justice Leagues deep in the Firestorm matrix and banding together all of the supervillains into a new Secret Society. But Lex Luthor wanted no part of that. So he banded together a few holdout villains – including Black Manta, Captain Cold, Black Adam, and Catwoman – and went toe-to-toe with the Syndicate.

After he won, Luthor was pardoned by the government and got himself a spot on the Justice League of America. The League initially mistrusted him, but he slowly earned their respect. After leaving the League, he witnessed Superman’s death, and adopted that identity in his absence. Now there's a new Superman in town, but Luthor's still wearing the sigil emblazoned on his chest.

Still a hero, miraculously.