I wholeheartedly disagree. Ntr is at its core about despair, and despair brings in turn jealousy and hatred. Revenge is the most natural course of events, or at least, attempt at revenge. A revenge ending isnt a cool getback which ends with fireworks and applause (that would actually be unbeliavable and ruin the theme). The mc will still remain heavily scarred with permanent changes to the way he sees others, mainly women. He still cant fuck a woman, seduce a woman like the antagonist. His psyche will always bear marks of inferiority, no matter how badly he managed to hurt the antagonist and even the women that betrayed him.Not true. Consistency is important in a story and many bad stories could have been good if the author had focused on presenting a consistent narrative. If your intent is to create an NTR focused story the second it crosses from NTR being the focus to revenge being the focus it stops being what you started out to create. If you want a revenge story then play or read one, but without a strong set up it's never going to be as satisfying as it could be. The HC games are about corruption, even the NTR is secondary to it. If you want just the revenge then play something else.
Revenge endings wouldnt ruin anything, they just have to be executed well, like all endings. Revenge isnt a different genra from ntr, it's a possible branching point or follow up.