Beginning his career as a circus performer where he helped train a young Hawkeye, Jacques DuQuesne later became the costumed mercenary Swordsman. He joined the Avengers, at first for nefarious reasons due to being a secret agent of HYDRA, but soon resolved to become a true Avenger after the Infinity Wars shook up his faith in his own morals.
Jacques Duquesne was a performer at various circuses and carnivals. His act demonstrated his mastery of knives, swords, and other bladed weapons. At one carnival he met a young Clint Barton. Seeing great potential in him, Swordsman and his partner, the original Trickshot, trained the boy in blades and archery respectively, with Clint often being a secondary performer in the Swordsman's act. Swordsman's gambling problem left him heavily in debt. One day the carnival paymaster was robbed, and Barton later found Swordsman with the money. Barton ran from him and climbed the high wire. Swordsman cut it by hurling his sword. Barton fell to the ground and the Swordsman left thinking he was dead. Barton survived and grew up to become Hawkeye.
Months later the circus went bankrupt and Jacques was forced to steal to survive. In addition to his skills in the circus, he was also a deserter of the French Special Forces, giving him special knowledge in the field of army combat. Jacques moved back to France where he began to establish his reputation as a mercenary and was eventually hired by HYDRA during its undercover phase when he went to Germany for a mission. Beyond his personal interests as a bounty hunter, Jacques aided Hydra to gain more prestige and became the best agent the organization. Months later he was reunited with Clint when S.H.I.E.L.D., then under secret control by HYDRA, tried to intercept an operation on a small terrorist organization, itself a project controlled by HYDRA though unknown to the S.H.I.E.L.D. agents involved to keep up the masquerade. The battle left Clint severely injured and nearly dead, though he soon recovered just in time to volunteer for watching over the Tesseract.
Due to his reputation, Jacques was the first to be chosen by Colonel Helmut Zemo to join his team of superhuman agents, being given his first mission to infiltrate the Avengers for a master plan... (cited from LoganWaynee)