The senior statesman of the agency, who had been running its enemy from inside it for years.
Alexander Pierce is the secretary of the World Security Council and, secretly, the director of Hydra inside S.H.I.E.L.D. Robert Redford plays him, and plays him as the most reasonable man in every room, which is the point: this is the film where the enemy is not an invasion but a policy.
The policy is Project Insight, built on an algorithm written by Arnim Zola that identifies anybody who might oppose Hydra so that they can be eliminated before they do. When Nick Fury starts looking into Insight’s files, Pierce sends the Winter Soldier to kill him, and then Steve Rogers. Rogers, Natasha Romanoff, Sam Wilson and the loyal remainder of S.H.I.E.L.D. stop the launch.
Minor spoiler
Fury kills him. Then, in Avengers: Endgame, the Avengers go back to 2012 for the Tesseract, and a Pierce from that year turns up after the Battle of New York to take Loki and the cube into custody from Stark and Thor. Wikipedia counts that as a variant from an alternate timeline rather than the same man, and so does this entry, which is why the film is in his list with that caveat.