Ronin (MCU)'s History
Clinton Francis "Clint" Barton, also known as Hawkeye, is a skilled marksman, a former special agent of S.H.I.E.L.D. and one of the founding members of the Avengers. Known for his use of the bow and arrow as his primary weapon, Barton had become one of the best agents of S.H.I.E.L.D., responsible for the recruitment of Black Widow, whom he developed a strong friendship with. Assigned by Nick Fury into watching over the Tesseract, he was brainwashed by Loki and used as a pawn for all his evil schemes. However, following their Attack on the Helicarrier, he was freed from Loki's mental control by Black Widow and joined the Avengers to fight against Loki's Chitauri army in the Battle of New York, ending Loki's Invasion before Hawkeye returned to his work as a S.H.I.E.L.D. agent.
Hawkeye continued to work for S.H.I.E.L.D. until its collapse following the HYDRA Uprising, he and the Avengers worked to bring down the remnants of HYDRA, eventually capturing Wolfgang von Strucker and ending the organization's threat to the world. However, Hawkeye was pulled back into the fight as Tony Stark had inadvertently used HYDRA as well as some Chitauri technology to create Ultron. As Ultron tried to destroy the world, he allied himself with Pietro and Wanda Maximoff and Barton focused much of his efforts in convincing them to change sides while keeping the Avengers safe by bringing them into his family home. During the final Battle of Sokovia, Hawkeye's life was saved by Quicksilver's sacrifice, resulting in Barton retiring from the Avengers to return to his family.
Despite living happily within retirement for a brief time, Barton was recruited by Captain America to aid him during his fight against the newly produced Sokovia Accords, which forced Rogers to protect his friend Bucky Barnes from being arrested for a crime he did not commit. Feeling that he owed a debt to Rogers and Maximoff, Hawkeye had joined in the Clash of the Avengers, fighting against Iron Man who was in support of the Accords. Despite putting up a good fight, Hawkeye and most of their team were eventually defeated and imprisoned at the Raft under the orders of Thaddeus Ross, only to be freed by Rogers. Barton returned back to retirement and, after striking a deal with Ross, was then placed under house arrest.
In the wake of the Decimation, Barton went on a grief-fuelled rampage against criminals for five years. Upon being tracked down by Natasha Romanoff, Barton was convinced to return to the Avengers to try and reverse the Decimation. Hawkeye joined the team in enacting the Time Heist in order to obtain all of the Infinity Stones, during which he witnessed Romanoff sacrifice her own life so Hawkeye could take the Soul Stone. However, just as the team succeeded in their goal, they were attacked by Thanos, as Hawkeye was ordered to ensure that Thanos could not obtain the Iron Gauntlet. Eventually, Thanos and his entire army were defeated once Tony Stark sacrificed his life, allowing Barton to return home as he reunited with his beloved family, while he still mourned Romanoff's death.