it's not really possible to have corruption and stay as a good guy. but there are shades of bad. like the mc can be a straight-up monster with no conscience, and some people like that. or you can have a delusional mc that honestly doesn't think he's evil while drugging mom to rape her. the latter is pretty much the real world version, as evil people almost never think they're evil. instead they rationalize it away with blaming the victim for inviting the abuse, or by convincing themselves that the victim is evil and thus a righteous target for anger. dehumanizing and demonizing the victim does wonders to silence that guilty conscience.
you could also make a 3rd party to take the responsiblity of forcing mc and someone dear to him do reprehensible things, like a hostage situation where a bank robber forces mom to suck mc off. then you build on that, making the victims realize they've actually began to like it and will be eventually doing it uncoerced. but that's a slightly different genre, real corruption typically revolves around mc getting thrills from crossing the forbidden lines.
in the end it isn't even about the victim but the fear+satisfaction mc gets from doing gradually more evil things. crossing the lines. so that's the ultimate reason mc can't stay a good guy in a corruption story. if you've never read hubert selby's 'demon', it would be a great example of this side of the equation, the mc corrupting himself.
the book 'demon' starts with a normal married office worker man, who first starts stealing pointless office supplies from work, then gets addicted to the thrill of it. he knows it's wrong but can't stop himself, so he gradually does worse and worse stuff, gets tangled in more lies, then just does it again. and that's the core of corruption really, the thrill doesn't necessarily come from turning mom into a slut, but the danger of getting caught or failing to get away with the ever worsening crimes the mc is drawn to commit.
and that's something that almost no games address, the thrill of surpassing the fear of getting caught. like 'demon' shows, it doesn't even have to have any sex involved. sex is kinda just the vanilla part of the corruption fetish.