4. Bucky Barnes
Yeah, I know. I'm going for another Winter Soldier character. This time however, it's the man himself. Bucky Barnes seemingly met his demise during the events of Captain America: The First Avenger. As we know though, he comes back in the next film as the titular Winter Soldier. A very complex character, Soldier starts off as an enemy of the Cap as well as all things S.H.I.E.L.D. Later though, he becomes one of his staunchest allies. That in mind, it has been questioned more than once where his loyalties are. Bucky's actor, Sebastian Stan, is also not a stranger to television. His latest credits include his award-winning turn in Political Animals, as well as in the ABC hit series Once Upon A Time, where he put in his turn as an unstable Mad Hatter. I'm sure if at all, an appearance by Bucky wouldn't come any time soon, but it would certainly be a great addition.