7. Thanos
Thanos has starred in so many fascinating comic book arcs - the Infinity Saga, Annihilation, The Thanos Imperative, Thanos Rising etc - that it would be hard to know which story to focus on in a movie based on the character, but surely that says everything about how good it could be. He is a mighty villain who doesn't do anything by half. When Thanos aims to conquer, he aims to do it on a universal scale - often looking to utilise items of immeasurable power such as the Infinity Gauntlet, the Cosmic Cube or the Heart of the Universe to do so - and a movie about his attempts to do exactly that, from his point of view, would be great. As an individual, Thanos is a mutant from the planet Titan who is obsessed with Death (on two levels - he wants to die and he also wants the attentions of Lady Death) and who possesses superhuman strength and durability which dwarves that of even Hulk and Thor, as well as a whole host of esoteric powers such as telepathy, telekinesis, teleportation, energy manipulation and matter transmutation - so there is nothing boring about him as a character either. If he is anything like his comic book portrayal when he appears properly on the big screen, he will be a massive threat to the entire Marvel Cinematic Universe and merely having him as a supporting character would be an enormous shame.