The leader of a violent mercenary team, in the film that gives Sam Wilson the shield for real.
Seth Voelker, also known as Sidewinder, is the leader of Serpent, a violent special ops team, and Giancarlo Esposito plays him in Captain America: Brave New World. That is the whole of what Wikipedia’s list says about him, and this entry does not add to it. The reader who sent this list described him as the leader of Serpent who later gained a grudge against Sam Wilson, and the grudge is recorded here as the reader’s reading of the film rather than as a fact from the page.