I am in the reworking phase myself. In this first phase, I am doing the research haha
You should think about the type of NTR you want to write about and what situation could exist to put a person in the spot where they are forced to deal with it.
The worst mistake I see game developers do is ignore real choices a person would have in a situation.
Take for example if a young couple are recently together and the guy finds out his wife is banging another guy.
He will probably just leave her and find someone else.
However, lets complicate that a bit more. They started dating in high school. Senior year he got kicked out of school and put on probation for a fight. Probation is 5 years. He also managed to get her pregnant. It's now 3 years later another child is on the way.
He's working at the only decent paying job in town running metal press in factory. It requires no skills and he is easily replaceable.
He needs the job to satisfy his probation and put food on the table for his child ...
He finds out from a coworker his boss has been bragging about banging his wife.
So he heads home sick one day and catches them in bed.
If you do this in the modern time frame. Cell phones exist and he could start using this time to collect evidence for a great divorce case and fuck his boss over down the road. But for the mean time he is stuck tolerating it. Push it back 50 years and would have to use film technology. Still can be done.
In real life worked at a location who did find out his friend was screwing his wife on days he would call in sick. He went home pulled shot gun out of the closet and killed both of them in bed. Sat on the front deck drinking bear till the police arrived. I think he spent the better part of six months in a mental hospital and that was about the extent of it. Temporary insanity. He only got away with it because the gun just happened to be their it was always loaded ... So he argued it was autonomous and no real thought was put behind it.
The fact is there are countless ways a jilted lover can get revenge on one or both parties. Most these games entirely ignore that aspect and don't consider writing anything in to explain why it doesn't happen or is not the option. Internal dialog is often a good method, have the character work through his thinking and rationality of the situation.
The guy above might be worried about getting caught leaving the one child without a father. He may not want to risk harming the child in the mom or just want to wait till after he is born.
That child in itself brings in a entire different question is it his. How long has this been going on? Maybe, both the kids are his bosses.
Getting revenge doesn't have to be some sort of direct confrontation. He could a range for his boss to have a work place accident or many others.
He could also take an entire different approach to everything choose to leave, fake his own death and frame the boss for it. It's a good possibility if he leaves evidence that his boss is sleeping with his wife.
If the guy supposedly likes his wife cheating that isn't NTR to me. If he is enabling her or any of this other stupid shit people write again not NTR.
Real NTR is about that helpless feeling of not being able to prevent it.
So you have to think about what's the best way to get the person in that spot or to feel he/she has no other choice but to endure it for whatever length of time.
You could always cripple the person make them a quadriplegic. Hell for that matter make his wife an entire fucking bitch. But he has to tolerate her because she is the only person taking care of him. She throws it in his face. Goes to the point of putting a TV in his room so he can see her being fucked in the other room. She turns it on forcing him to watch he has no way to turn it off or change channel or even fall asleep. She has the volume up on loud to prevent that.
So does he get better some how. Kill himself. Family show up and get him help....? Or does the bitch go over board he dies and she goes to jail for neglect ... Maybe, she is fucking his doctor and since he is under doctors care it won't even require an autopsy.
It isn't hard to come up with situations in which someone mentally justify enduring it for some length of time.
To many authors resort to stupid shit like blackmail. It next to never works in real life and most authors can't even write it decent enough to make it believable. It's more likely you will produce another shit game than pull of using blackmail correctly.