Story Identification: Spy story in Space; the hero receives implants of relevant memories / identities

Question

Trying to identify the story; it's in 4 or so parts (I would guess published as a serial), and the hero is some form of space-age Spy.

Spies of his nature were EXTREMELY undercover, usually, are given memory implants of specific people (either who they are seeking, or someone they are imitating), and pseudo skin and such, as needed. They are conditioned to respond as the person they are done up as, this conditioning only breaking down under extreme conditions. They are refered to as 'Prime-Operators' or some such; if one should die or go missing, an entire planet could be faced with extinction as a reprisal.

There are several stories I recall; the first involved aliens that, after something was done to them, lived at an exteremely slow pace -- the horror came when a human had this done to him at the end, after being stabbed. (The hero was wounded, but lived.) The plot involved some action being taken by the people running the facility on the planet that was resulting in excellent output, but at the cost of the natives dying quickly, due to a powder they were being dosed with via their barefeet and the floor of the mine.

Another story had the hero taking the personality of a man who was a member of the nobility on some planet, but this one broke down quickly due to unforseen circumstances. He spends a chunk of it in jail/prison and takes a leave afterwards with the women he was stuck with.

In the end, the hero was sufficiently conflicted by all of the horrific things he had to do, that they end up wiping his mind or killing him at the very end.

The cover of the paperback copy I once had was of a man, on his knees, leaning back in horror, as various masks litter the ground near him. Based on that description, searchings keep bring me to 'Today We Choose Faces', which, although a good story, is NOT the one I'm looking for.

Answer 1

I think this must be "All My Sins Remembered" by Joe Haldeman.
Amazon link

Once Otto McGavin was a kind and gentle soul; then he was recruited by the all-powerful Confederación. An ultrasecretive, government-linked organization, the Confederación’s stated mission of protecting threatened life, both human and alien, throughout the galaxy greatly appeals to the Anglo-Buddhist McGavin as he eagerly prepares to embark on a career of diplomacy and selfless works. But Otto’s new masters have other plans for the idealistic young recruit. Through a process of immersion therapy and hypnosis, and by encasing him in temporary bodies of plastiflesh, scientists can overlay Otto’s true persona with other ones, transforming him completely—body, mind, and soul—into the ruthlessly effective prime operator the Confederación wants him to be. But decades of interstellar subterfuge and violence, and years spent wearing the personae of spies and cold-blooded killers, must ultimately take their toll—and before he leaves behind the lives that have been cruelly thrust upon him, Otto McGavin will have to somehow come to terms with who he really is and the monstrous things he has done.