Trelane: No, not in Starfleet, not interested in terror.
Colonel Green: Possible, they'd have to play with the timeline a bit by our reckoning but it hardly matters in the new reality.
Khan: Wasn't a terrorist, wasn't a one man weapon of mass destruction, wasn't in Starfleet....nope, definitely not Khan.
Garth: Has the ability and power to destroy Starfleet from within, he may have gained some power after becoming a megalomaniac.
Gary Mitchell: In Starfleet. Wanted to create worlds in his own image. Gained god-like power. May have a vendetta against Starfleet/Kirk for trying to stop him. Mentioned by an insider as one of the names that might be in the movie.
Ben Finney: Sabotaged a starship for revenge. In Starfleet, no special powers.
My possibility ratings:
Colonel Green or associates: 20%