A lot was lost by the end of Avengers: Infinity War. And by "a lot," we mean half the universe's population. In an instant, after Thanos snapped his fingers wearing the Infinity Gauntlet holding all six Infinity Stones, people everywhere turned to dust, including a big chunk of Avengers. But, as the newest Endgame trailer suggests, the Avengers aren't just struggling with the loss of teammates, but of family members. In fact, one theory suggests that Hawkeye's family died in the Infinity War snap, which would explain Clint Barton's more sober demeanor, along with his edgy haircut.
As noted by ComicBook.com, nothing in the newest Avengers: Endgame trailer flat out states that Barton's family disappeared in the snap. But the shot of him teaching a young girl, presumably his daughter, archery (or giving her tips) and his smiling, joyous face is a stark contrast to the later view of him in the rain with half his head shaved. And seeing those two images of Hawkeye back to back definitely suggests that he's suffered no small trauma since fans last saw him in Captain America: Civil War. In fact, Many fans have already theorized that Hawkeye's new look is the introduction of Ronin, a new, grittier, iteration of the character. And losing his family, or even just part of it, to Thanos could certainly trigger that kind of huge transformation in the character.
Before getting into who Ronin is, a Reddit user made a good observation from the recently released Endgame trailer. User armablo posted a photo from the part of the trailer where Clint is teaching his daughter how to shoot an arrow. As the user pointed out, there's something around his right ankle, what looks like it could be an ankle monitor. This makes sense, as both he and Scott Lang made a deal with the government to refrain from vigilante activity and returned to their families on house arrest after Civil War. It also puts this scene decidedly in a time pre-snap, as Scott is seen getting his ankle monitor removed before he becomes aware of the snap in the Ant-Man and the Wasp post-credits scene.
And, if this scene is, in fact, pre-snap, then it stands to reason that his family isn't doing too well after the events of Infinity War. And, if that's true, then it makes sense that Hawkeye would become Ronin. In the comics, Ronin is one of Hawkeye's identities, originally helmed by Maya Lopez, aka Echo. She took up the mantle of "Ronin" as an alias to protect her identity. In the comics, she was an assassin who then fought crime with the Avengers, but was killed because of her investigation into the Hand and Elektra and Clint Barton took up the position as Ronin after she died.
If Clint is Ronin in Avengers 4, then he's no longer an Avenger, he's an assassin. And, though all of this has yet to be confirmed, even the thought of Hawkeye's family disappearing in the snap has fans all in their feelings on Twitter.
Thanos' snap really did a number on the whole world and then some, so Barton's family might very well be another casualty to this war. The question now is, what are Hawkeye and the Avengers going to do about it?