Crossbones

Brock Rumlow, also known as Crossbones, is a recurring antagonist in the Marvel Cinematic Universe, appearing as a major antagonist in Captain America: The Winter Soldier and the opening antagonist of Captain America: Civil War, while his 2012 self appears as a minor antagonist in Avengers: Endgame. A variant of him also serves as a minor antagonist in "What If... the World Lost Its Mightiest Heroes?", the third episode of the Marvel animated anthology series What If...?.
He is an agent of HYDRA who initially posed as the leader of S.H.I.E.L.D.'s counter terrorism team known as STRIKE, and an enemy of Captain America and the Avengers.
He was portrayed by Frank Grillo.