Brock Rumlow, also known as Crossbones, is a villainous character in Marvel Comics and has primarily been an enemy of Captain America. In the comics, he has been portrayed as a ruthless mercenary and terrorist, willing to work for any criminal organization on the promise of a fat paycheck and a large body count.
In the Marvel Cinematic Universe, Rumlow (portrayed by Frank Grillo) was a HYDRA agent working inside S.H.I.E.L.D. as the leader of its STRIKE unit. He was a no-nonsense operative who strongly believed in the order that HYDRA intended to bring to the world, but after suffering terrible injuries during the Battle of the Triskelion, he abandoned HYDRA's doctrine and became focused solely on revenge.
Captain America: The Winter Soldier[]
After the attempted assassination of Nick Fury, Rumlow was charged by Alexander Pierce in detaining Captain Steve Rogers before he could leave the Triskelion. He and several other STRIKE members, all of whom were undercover HYDRA operatives, attempted to ambush Rogers in an elevator, but the enhanced Rogers was the superior fighter and tactician, and was able to beat them all into unconsciousness and escape.
Afterwards, Rumlow gathered his STRIKE team members and they all organized a manhunt for Captain America and Black Widow in an attempt to prevent Project Insight from being compromised. They were able to track the two of them into a mall in Washington D.C. but they couldn't find them after a long search.
Later on, Rogers and Romanoff were discovered at Camp Lehigh where the digitized consciousness of Arnim Zola was distracting the two. Pierce ordered a missile strike and had the camp destroyed. Soon afterwards, Rumlow and his STRIKE team were deployed to confirm if the two of them were killed at the ruins of the camp. He eventually discovered their footprints and confirmed that they were alive and so he had to call in the Winter Soldier, the most elite assassin and agent of HYDRA. Brock would remain inactive until the end of a battle between the Winter Soldier with his HYDRA team and Captain America with Black Widow and Falcon.
After the battle, Rumlow ran into the event with his STRIKE team and successfully captured all three of them. After the three of them had surrendered, he had noticed his subordinate, Jack Rollins, attempting to execute Captain America, but called it off to prevent media attention and told him to wait until they were cleared of media interference. Eventually, when the coast was clear, he ordered three graves dug, but the three of them had escaped and he eventually went back to a secret HYDRA base where the Winter Soldier was seen being managed. He then watched as Bucky mentioned that he knew Rogers and Pierce ordered his memories wiped so he could defeat Captain America.
Meanwhile back at the Triskelion, Rumlow appeared and held Cameron Klein at gunpoint which caused agent Sharon Carter to do the same to Brock. He feigned surrender before pulling out a knife and stabbed her hand and soon a gunfight between S.H.I.E.L.D. and HYDRA agents broke out while Rumlow accessed the computers to launch Project Insight Helicarriers. He succeeded and soon the Helicarriers were brought into the air and he escaped while HYDRA sleeper agents launch an attack on S.H.I.E.L.D. and brought down the agency. On his way through the Triskelion, Rumlow ran into several S.H.I.E.L.D. agents and killed them by both stabbing and gunning them down with their weapons when he got a call.
He received a call where he was informed that Alexander Pierce was captured by Captain America, Black Widow, and Falcon and that he had to rescue him to prevent HYDRA's plans from being compromised. As he went to save Pierce, he was attacked by Falcon and engaged in a fight with him. Rumlow was superior to Falcon and bragged about HYDRA's imminent victory and they continued fighting until a crashing Helicarrier came through the building and rubble and debris fell on Rumlow, crushing him. He survived, but had received heavy amounts of scars and burns across his whole body.
Captain America: Civil War[]
In the time since the Battle of the Triskelion, Rumlow had taken on the criminal alias "Crossbones" and was no longer working for HYDRA. Having become unhinged and obsessed with revenge, he had become a brutal mercenary and anarchist.
In 2016, Rumlow had assembled a group of mercenaries and launched an attack on the Institute for Infectious Diseases in Lagos, Nigeria. Their objective was to steal a biological weapon, though it is unknown if they intended to use it themselves or sell it off. Captain America and the Avengers were in hot pursuit and engaged Crossbones' men outside the IFID building, but Crossbones and some of his mercs had managed to get away with a vial containing a deadly virus. The escapees split up to throw off their pursuers, though Black Widow and Falcon succeeded in taking down the mercenary carrying the vial and recovered it before the virus could be released.
Meanwhile, Crossbones was pursued by Captain America and attempted to take his long-awaited revenge. Equipped with a hardened battlesuit and hydraulic gauntlets, Crossbones was almost a match for the captain, but with every hit he dodged, Rogers was able to dismantle part of Crossbones' suit and eventually brought the terrorist to his knees, removing his mask and revealing the horrendous scars covering Rumlow's face.
Defeated, Rumlow revealed to Rogers that Bucky Barnes had briefly recovered his memory before HYDRA suppressed it yet again. He then activated a bomb contained in his suit, intent on committing suicide and taking Captain America with him. Just as Rumlow's bomb went off, Scarlet Witch appeared and used her telekinetic powers to try and contain the explosion. Unable to hold it, Wanda levitated the exploding Rumlow into the air before releasing him. However, the explosion was released in close proximity to a building, resulting in 26 civilian deaths and several more injured.