I personally think that a couple of the Bad Endings will lead to FV being successful. It'll appeal to the NTR fans and just allow consequences for weak MC actions.
I like NTR games myself if they they written well. It's just that most of them are just "other person has magic penis" which I don't like
You may not have seen my initial predictions (I don't remember if I shared these ones specifically), but I think a couple of bad endings will be
1.) FV is successful in doing something to Lacey, and MC loses it and murders them (if you have high love)
2.) FV is successful in doing something to Lacey because MC is unsupportive of her. He keeps reminding her that she's worthless and toxic, and she breaks, taking Special K (low bad_guy/low love)
3.) MC makes Lacey seduce/fuck people to get information to defeat the NTR Villains. (not necessarily a bad ending, but still NTR. I think it is set up by the Jealousy Date and MC's thoughts during the No Fun path.)
4.) I think that at some point in the story, Isaac will have a chance to prove if he will try to take Lacey or not. It's hinted that even though Isaac claims he wouldn't do that, that people don't really know how they will act until they get the opportunity. I think this would be like, Low Isaac score (to make him decide to chase his own selfish desires) and low love/low bad guy (to make Lacey decide to just escape from it all)
Those are all the NTR endings that I think could potentially happen
I do think it's important to note that all these endings would result from MC being unsupportive to Lacey, telling her she's of no value and making her feel like she is toxic to MC (she is, but it'd make her give up on herself)