15. Neron
Demons have not had a lot of success in superhero films. Hellboy is probably the only superhero film series that has successfully featured demonic villains in all their horrifying glory. One of the big issues, sadly, is that these otherwordly, enigmatic entities are reduced to roaring, screaming monsters who just run around and get blown up. No nuance. They're pure evil, and, sadly, not all that interesting. Neron, however, plays a more Faustian role in the DC Universe. His most famous story, Underworld Unleashed, has him grant numerous villains their greatest desires in a plot to take over the world. He is temptation, and works through other characters. He'd serve as a marvelous Big Bad, unleashing pandemonium and insanely massive traps for the heroes and the world. The Justice League would be forced to confront super villains who now have the means to destroy the League for good.