Mack

Alphonso "Mack" Mackenzie is a S.H.I.E.L.D. mechanic and field agent who joins the team in its second season and becomes one of its most steady presences, eventually rising to lead the agency himself. He is S.H.I.E.L.D.'s director by the time the series ends.

First turns up in Agents of S.H.I.E.L.D. (Season 4).