3. Franklin Hall (Agents of S.H.I.E.L.D)
In the third episode of Agents of S.H.I.E.L.D ("The Asset"), Franklin Hall (who is the S.H.I.E.L.D asset in question) gets kidnapped by his former research partner Ian Quinn. Quinn intends to use Hall to take control over the planet's gravity by building a giant "gravitonium" generator. S.H.I.E.L.D agent Skye heads to Malta with the team to infiltrate Quinn's mansion so that Phil Coulson and Grant Ward can rescue Hall. Skye tricks Quinn into believing that she is betraying S.H.I.E.L.D on behalf of the Rising Tide in order to get his guard down. However, Coulson soon discovers that Hall wants to destroy the massive gravity device, but Coulson warns him doing so would end up killing millions. Their disagreement becomes quite violent and ultimately forces Coulson to not save Hall as he falls into the middle of the generator, seemingly vaporising him. However, at the end of the episode, a hand emerges from the device, indicating that Hall may still be alive. If Franklin Hall was to somehow return to the MCU as his comic book namesake Graviton, it would be absolutely awesome - whether it be in a movie or on television - because he is a fantastic villain.