Crossbones

Brock Rumlow, also known as Crossbones, is an agent of S.H.I.E.L.D. and a world-class hand-to-hand fighter with an extensive experience in street-fighting and various martial arts and military combat techniques.

Biography
Brock Rumlow was an agent of S.H.I.E.L.D. who was often partnered with Captain America and the Black Widow.

One operation saw Rumlow assisting in the recovery of the stolen Zodiac weapon and the apprehension of the terrorists that stole it.

Relationships

 * Captain America - Former Ally

Trivia

 * In Marvel Comics, Crossbones is an agent of the Red Skull.