You are probably asking because you haven't found any games that has this as the core theme. I can't really recall any off the top of my head either.
The vast majority of devs want their male MC to be somewhat relatable and a generally nice guy.
A decent amount of them give an option for them to be "good/evil," but it almost never depicts the gradual moral degeneration brought on by some plot specific event. It's more like, "is your MC is a simp or a giant creepy asshole?" dichotomy.
A small subset is about rapist MCs that are unequivocally self aware and evil, but again, they start off that way and you don't see the corruption arcs.
That said, I remembered one game that might fit the bill. It's Anax's earlier game, and one of the only ones that feature a male MC from him.
https://f95zone.to/threads/cult-of-corruption-the-summoning-anaximanes.5919/
It's not for everyone. None of his games are. They all have this grotesque horror porn transformation type of thing going on. But he is a talented writer for sure. You could give it a spin.
But I really do feel like there is a great story to be told in a more contemporary setting. Where a good guy MC is put into circumstances where he has to take increasingly morally questionable decisions for a noble goal, eventually being consumed by the abyss and becoming the very thing he is fighting against. Something like that. Most naturally, I picture some gang related story. Perhaps some undercover cop story. Ah well.
