Yeah, there are several different pathologies associated with the term "psychopath", but I'm referring to actual psychopaths. The parts of their brain that are associated with emotional connection with other human beings are never activated, some researchers tested it with, if I remember correctly, MRI machines, where those parts of the brain simply have no activity where all neurotypical people do have activity. The ones who have some degree of social intelligence (the ones who avoid getting found out as children) learn to mimic human behaviors and emotions, and engage in performative behaviors to get things out of people. Zach exhibits textbook psychopathic tendencies, based on his behaviors, on his fake public persona, and the actions he takes across the game. These kinds of people don't change, any more than a person with severe spinal trauma gets up out of their wheelchair and starts running a marathon some day.
But like I said a couple of pages ago; it's first and foremost a porn game, and one that has divergent narratives and multiple endings. If people like this ending for whatever other reasons they like it, then that's totally fine. It doesn't have to make sense for many people to enjoy it. It's just that it seemed like the script followed a very plausible bent, until very suddenly right at the end, Zach becomes a completely different person, which was really weird. Maybe alien abductions are real in this fictional universe, who knows.
Psychopath is not synonymous with serial killer. More socially aware psychopaths are often law abiding, because they understand cause and effect, and like most human beings, still follow incentives.
If you think that blackmailing people, enjoying other people's pain non-consensually, striving to break up a marriage, manipulating everyone at every turn, cheating without remorse, using and discarding people when it suits you, feigning remorse when it suits you but being a totally different person in private, intentionally setting up scenarios to abuse and humiliate people, and then doing everything you can for years later to rub all of this in the face of the person whose life you ruined, is normal behavior, then there's not much more to discuss. It obviously isn't.