There are some NTR stories that do show the consequences of said actions. However, just not this kind of consequences. Most of the time when they do have consequences and the Bad guy's get their just desserts the Person who gets cucked ends up having to deal with the damaged goods, and said goods ends up cheating again due to no longer being satisfied
Hmm, most of the isekai or time-travel works I've read (that involve the traveller seeking redemption) have the MC feeling regret for not being proactive enough in their life or failing to prevent some catastrophe. I don't think I've read one where the MC was the direct cause of the catastrophe. So the premise is really interesting.