Marcus Scarlotti is a mercenary with long-standing links to HYDRA who undertakes a contract to tarnish the reputation of S.H.I.E.L.D. and turn the world against the heroes. To this end, he and his team attack the U.N. in S.H.I.E.L.D. uniforms and use Diviner Disks to kill a number of delegates present, all the while proclaiming S.H.I.E.L.D.'s determination to step out of the shadows. They are, of course, part of a more complex and layered plot, conceived (seemingly) by Dr. Daniel Whitehall, using a Belgian minister and his apparent opposition to the anti-S.H.I.E.L.D. stance of Senator Christian Ward to lure S.H.I.E.L.D. agents to that country and out of hiding. Scarlotti and his mercs take down and kill a team of six, basically from ambush, and are in turn defeated by Lance Hunter, Bobbi Morse and Melinda May.
When last seen, Scarlotti was being dragged off in the custody of General Glenn Talbot's troops, so when and if he will return is a matter of speculation. As of Season 5 there have been no further sightings.