Expert spy Sharon Carter’s loyalties lay with her country, but she will bend the rules if it’s something she believes, even while working for government-backed agencies, such as S.H.I.E.L.D. and the CIA.
Sharon grows up idolizing her great-aunt Margaret “Peggy” Carter, legendary spy and co-founder of S.H.I.E.L.D. Seeing a photograph of her great-aunt with JFK, Carter thinks she has a pretty cool aunt. When Sharon grows up, Peggy encourages her niece’s career in espionage by purchasing her first thigh holster, while Carter’s mother opposes her enlistment in S.H.I.E.L.D.
As a S.H.I.E.L.D. agent, Carter is trained in undercover work and becomes an expert spy. She is also trained in armed and unarmed combat and is a skilled fighter. She is a master marksman, possessing adaptability to various firearms. At S.H.I.E.L.D., and later while working with the CIA, she has access to numerous assets, resources, and anything within their custody.
Carter’s enemies are typically the same enemies of S.H.I.E.L.D., such as the terrorist organization Hydra who infiltrates the ranks at the agency. She faces former allies such as Brock Rumlow when he turns out to be a double agent for Hydra.
Some of her opponents are temporary, like James Buchanan Barnes, AKA Winter Soldier, when he becomes mind-controlled. Ongoing enemies include Zemo, a colonel for the Sokovian special forces, responsible for activating Barnes’ Winter Soldier programming and for the events that lead to a civil war between the Avengers.
Carter looks up to her great-aunt Peggy Carter, the legendary co-founder of S.H.I.E.L.D. She refrains from sharing her relation to Peggy since she didn’t want to live up to such high expectations.
Under order from S.H.I.E.L.D. director Nick Fury, Carter meets Steve Rogers, AKA Captain America, while posing as his next-door neighbor. During the assignment, Rogers flirts with her and a mutual romantic interest blooms between them. Carter later aides Rogers and his ally Sam Wilson, AKA Falcon, in their search for the Winter Soldier when Zemo frames him for a bombing. Carter goes out of her way to help Rogers.
Alongside fellow S.H.I.E.L.D. agent Natasha Romanoff, AKA Black Widow, she fights a mind-controlled Barnes to prevent him from escaping custody at the Joint Counter Terrorist Centre in Berlin.
Taking orders from Nick Fury, Sharon received an assignment to protect Steve Rogers and posed as his next-door neighbor “Kate,” a nurse. One day as she was headed to finish her laundry, she runs into him in the hallway. He offered her his machine instead and invited her out to coffee. She politely declined and told him that he may have left his stereo on, and departed to do the rest of her laundry.
Back in Berlin, Carter joined Ross who greeted the captured Rogers, Wilson, Barnes, and T’Challa, who all had been fighting and causing destruction in a rather public way. Ross ordered her to take their equipment and lock it up. Carter then joined Wilson and Rogers in a conference room, giving Wilson a receipt for his gear (He, needless to say, was offended by the receipt and how his advanced set of wings was labeled as a “bird costume.”) In the room, there was video feed of Barnes’ interrogation which was simultaneously occurring. Looking around for any superiors, Carter turned on the audio. Rogers questioned her about the situation, asking why the authorities would release Barnes’ photo at all and she replied to get the word out. Rogers suggested that it was a good way to flush a guy out and she realized someone framed him to find him. In their discussion, Carter also realized that it didn’t guarantee that he would be captured by the person that framed him, but it would ensure his capture by them. They turned their attention back to the feed at the interrogator who they’d later find out was actually Zemo, a Sokovian bent on revenge against the Avengers and at that very moment was using Barnes’ Winter Soldier programming against him. Suddenly, the electricity went out at the facility, disconnecting the interrogation feed. Carter told them Barnes’ location, to which Rogers and Wilson rushed down to him.
After Thanos gathered all the Infinity Stones and snapped away half of the universe’s living creatures from existence, Carter was one of them. She returned five years later after the Avengers had obtained the Stones and reversed Thanos’ Snap that caused the Blip.