Avengers 4 Trailer Decoded: Every Character Analysed & Explored
6. Ronin/Hawkeye (Jeremy Renner)
He might not have been in the first part of this movie double-header thanks to being under house arrest, but Clint Barton has a major role to play in Avengers: Endgame, but he's going to have to come out of a place of severe darkness first.
As was revealed a long time ago now, Barton will be dropping his wholesome Hawkeye gimmick and taking on the Ronin guise of the comics. Thanks to his placement in the trailer - exactly at the point Cap says "we lost family" - it would appear that he adopts that new persona after losing his family to the snap. It's left him darker, broken and very, very angry, hence the move to close quarter weapons like swords - almost like he wants to see the whites of the eyes of those he kills.
The fact that he's in Japan (reportedly killing yakuza) would suggest he is still working for the government (or someone at least), perhaps filling the void inside him with the only other thing he knows - government-sanctioned killing. And it should come down to Black Widow to tell him of the plan to undo what Thanos did and re-recruit him to the team.
Expect nobody to relish Thanos' defeat more than him.