Crossbones

Crossbones is an enemy of Captain America in the comics. In the film Captain America: The Winter Soldier, he is an assassin who works for Alexander Pierce and HYDRA as a sleeper agent within S.H.I.E.L.D. He is the tertiary antagonist of the film.

Abilities
Crossbones is one of the world's best hand-to-hand combatants, with extensive training in street-fighting, military combatives, and various forms of martial arts, He has trained extensively with the Taskmaster to the point where he was actually made an instructor at the Taskmaster's school for criminals. Crossbones is also a superior marksman with guns, crossbows, and throwing knives. He also has some experience with torture and brainwashing, having effectively "reprogrammed" Sin and nearly so with Diamondback. He is also an expert pilot.

Strength level
Peak human

Weaknesses
That of a normal human.

Avengers Assemble
He appeared in Avengers Assemble, he was captured by the Avengers and ordered to tell where the Red Skull is hiding. While Captain America wore his costume to infiltrate Cabal.

Captain America: The Winter Soldier
Rumlow alongside Captain America and Black Widow were sent to retrieve the Lemurian Star, a ship of SHIELD who was captured by mercenaries led by Georges Batroc. The mission was a success because they recovered the Lemurian and captured Batroc.

Later, Rumlow led Strike team whose mission was to capture Rogers because Pierce declared Rogers an enemy of SHIELD. Rogers manages to escapes on numerous ocassions of Rumlow and his team but thanks to the help of the Winter Soldier, Strike captures Rogers, Wilson and Romanoff. When Jack Rollins wanted to shoot Rogers, Rumlow stopped him saying it was not the place to do it. Then, they brought the fugitives to a place where these execute them but Rogers, Romanoff and Wilson escapes thanks to Maria Hill.

After Rogers said that HYDRA was still alive, Rumlow managed to put one Helicarrier in orbit despite the interference of a man in a control, who threatened to kill him and agent Carter. Later, Rumlow fight with Falcon, which survives an explosion caused by the crash of a Helicarrier against a building.