10 Marvel Cinematic Universe Villains Who Need To Make A Comeback

5. Graviton

Appeared In: Agents of S.H.I.E.L.D.: Season 1. Just three episodes into its run, Agents of S.H.I.E.L.D. set up Dr. Franklin Hall as the villainous Graviton. The show subsequently spent the rest of the season teasing his reemergence straight through to its finale, which saw the Gravitonium containing Hall in the hands of recurring antagonist Ian Quinn. And then, just like that, nothing ever came of it. Throughout the show's second season and its currently-airing third, we haven't heard from or seen Hall/Graviton at all, with the series seemingly dropping the season-long thread entirely to make way for bigger things like more HYDRA and the Inhumans. Recently, though, the seemingly one-off character of the Asgardian Elliot Randolph returned for the show's third season, and if he can return, then there's no reason Graviton - and the also-MIA Quinn, for that matter - can show up sooner than later in order to finally pay off one of the first season's biggest setups.