Has the amateur Metroidvania/Castleroid game Nightmare Sphere been mentioned yet? I don't really have images I can post, but I will say that this game does have a soul corrupting system, in which as Relm (the heroine) kills demons or gets raped by them, her soul becomes polluted, which at its maximum, traps her in a state where any humans she comes across she'll kill if her attacks hit them, plus it gives her the ability to rape downed humans (awkward but nice way to restore health
).