Joseph Huntsman, aka the Shadow Reaper, is a freelance agent for the CIA.
We are given the strong impression that Huntsman has and does still do work for other agencies, all likely a Five Eyes member but we also are shown that all the violent and stressful things he has been asked to do over the many years he has been active have all come with a price and the thought of another mission is meant with sorrow that such things still need to be done.
Huntsman's legacy as 'The Shadow Reaper' has proceeded him to those with the need to know but he is "unknown to most of the world's population, known very well to those who need him, and those who should fear him". That reputation is a powerful one as we hear people talking about him saying that "the Shadow Reaper was a force to be reckoned with, and the enemies of the free world would once again soon bear witness to his deadly alliance with fate".
"He stood tall, a figure forged in the fires of battle, ready to confront the face of evil" with "rugged features, etched with the marks of countless battles" making people "marvel at the man's resilience". "There was an aura of danger that clung to him, a silent threat that hung in the air like an electric charge. Huntsman's eyes, sharp and penetrating, held a world of knowledge and experience, an intricate tapestry of secrets and shadows that only he could decipher".
One last quote about his skillset: "he knew that his skills were unmatched, his reputation forged in the crucible of dangerous missions. He was the one they turned to when all hope seemed lost".
Huntsman is not always brought in just to kill someone but he is usually summoned when there is someone to be found with a great chance (okay, certainty) that people involved are going to die at his hands. After receiving his briefing and accepting the first recorded mission, Huntsman tells those asking for his help, just before leaving the room, "In the realm of shadows, I am forever accompanied."