Crossbones

Brock Rumlow was a HYDRA agent within S.H.I.E.L.D, briefly worked in the New Invaders alongside Captain America, and is a STRIKE team commander. He was a world-class hand-to-hand combatant, with extensive experience in various street fighting, martial arts, and military combat techniques. During the HYDRA Uprising, Rumlow was ordered to lead the HYDRA team and assassinate Captain America, until Rumlow was nearly killed during the Battle at the Triskelion, gaining horrific facial scars.

Once he recovered, and hearing that Alexander Pierce had died, Rumlow escaped from the hospital and, assuming the codename Crossbones, became a terrorist leading his own strike force, but he set out on a path to exact revenge and make anyone involved in his downfall suffer the same pain and loss he endured. He lured the Avengers into a public fight in which he personally fought Captain America. Although he was defeated, Crossbones activated a bomb hidden within his suit and, despite Scarlet Witch's best efforts to contain the blast, killed himself and dozens of innocent people in the resulting explosion.

At The End of Infinity Wars, Adam Warlock attempted to bring back the fallen heroes. But since he was inexperienced with the powers of the Infinity Stones, he revived tons of characters including Rumlow.

Since HYDRA's defeat crumbling, he has joined the Masters of Evil where he serves as one of the Lead Enforcers.