It all goes back to 2004, when the original Avengers comic ended in the event called "Avengers Disassembled." The team reformed a few months later as The New Avengers. One of the newer members was a mysterious ninja, clad all in black and gold, wielding two katana samurai swords. Calling themselves "Ronin," which translates to "Samurai without a master," the character of Ronin was eventually revealed to be Maya Lopez, also called Echo, who was a DaredevilÂ supporting character and one of Marvel's few deaf superheroes.But after Maya dropped the Ronin identity, the mantle was picked up by none other than Clint Barton. At the time of the "Avengers Disassembled" event, Hawkeye was killed when the Scarlet Witch, who had ost touch with reality, creating a chaotic situation that forced Clint to sacrifice himself to save his teammates. The Scarlet Witch later altered reality yet again, only this time, she changed it so that Clint was alive and well. Upon returning to life, Clint adopted Echo's newly abandoned Ronin costume and identity.As Ronin, Clint joined the cast of New Avengers, even though many of the other members didn't really even know who he was at first, as his resurrection wasn't publicly known by everyone. Wanting answers to his death and resurrection, Ronin then headed to Eastern Europe to confront the Scarlet Witch about his temporary death and subsequent resurrection at her hands, but instead began a romantic relationship with her when he discovered that she has no memory of the events, nor any powers. After few years of kicking bad guy ass as Ronin, Clint then eventually switched back to his Hawkeye identity, which he's kept ever since.So what does this mean for Avengers: Endgame? The safest assumption is that Clint lost his entire family as part of the Thanos' "decimation" of the universe, as it's now officially called, and in his grief and rage has turned to his a new identity as Ronin. Judging from his facial expression, this is a man who has lost it all, and has gone down a much darker path, one that involves more swords and less arrows, and now has the identity to match. Whether he returns to the Hawkeye identity in the movies just as he did in the comics is now anyone's guess.
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