The team's muscle, recruited young by the man who trained him, who was never working for the people he said he was.
Grant Douglas Ward is the son of politicians, abused as a child by his parents and his older brother Christian. After trying to kill Christian by burning their house down, he meets John Garrett, a Hydra double agent inside S.H.I.E.L.D., who trains him into a skilled agent. He is assigned to Coulson’s team as its muscle and wetwork specialist. Brett Dalton plays him.
Agents of S.H.I.E.L.D. spends most of a season being a competent, unexciting procedural, and then Captain America: The Winter Soldier reveals Hydra inside S.H.I.E.L.D. and the series has to answer it. Ward is the answer, and it is the only time the television tier and the films ever moved together properly.