This is the most important part about NTR that a lot of NTR AVNs seemingly forget: NTR is about your gf/wife being stolen from you, not about the wife being sexually "corrupted".
Zach successfully steals Sophie from Felix in one of the endings (the "A Better Life" ending, where she marries Zach and has three kids with him) - in that one, there is no hint that she turned into a 'slut', instead, she becomes a loving wife & mother to her new family with the NTR antagonist. That right there is the true essence of NTR, while the rest are the "standard" NTR corruption games that show the breaking of that mind 'barrier' in the woman and turn her into a nymphomaniac.
Zach showed Sophie a world of pleasure she was missing out on by being "blinded" by her love for Felix. Once Sophie realized she wasn't ever going to be truly satisfied with what Felix was able to offer her, she left him. Cruelly, but she left him for a "better" man. Peak NTR.