1) Bucky’s Capitulation
At the end of Civil War, after two hours-plus of running from authorities and fighting off superhumans, Bucky Barnes has Steve Rogers re-freeze him, deep inside a facility in Wakanda. His reasoning is that he’s just too dangerous to remain conscious and free any longer; which, all things considered, is pretty sound (if extreme) logic. It begs one question, though: why does Bucky resist in the first place?
The question is an important one, because Bucky deciding to run near the start of Civil War sets in motion the plot of the entire film. The reason we have two-and-a-half-hours of movie, and the reason why the Avengers split and fight, is because Bucky chooses not to be taken in. Cap defies Stark and half of the Avengers in order to prevent them from taking Bucky away – only for him to later sit back and watch, as Bucky willingly puts himself back into deep freeze.