1) bad writing/poor translations 2) unrealistic and/or overly used character models 3) no skip option for fetishes not my jam or similarly being forced into a character path I don't want just to advance the main story (looking at you every incest game- I'm not Mars, I don't need moms)
NTR for sure, bestiality, unrealistic body proportions (like astronomically huge breasts, or something like a smol having a ridiculously large dick), scat, vore/gore/torture. Those just take all the interest I had for a game through the window instantly.
A dumb, stupid, creepy or pathetic mc. A MC that acts like a 15 year old virgin seeing boobies for the first time.
When the dev starts confusing he/she.
When a LI goes on about how much they love the MC and then proceeds to fuck one of the other LI's. <-- dropped a game for this exact reason.
Unexpected kinks I dislike or kinks the dev said would not happen.
Forced sex that we can't avoid with certain characters.
NTR
Too many love interests
Too many routes to replay
Game over's and too grindy sandboxes.
Probably a few more things that currently do not come to mind.
Grinding
When the plot doesn't make any sense
When characters that met 5minutes ago are already fucking without any reason because the dev can't bother writing more than 5minutes of plot between each sex scene or the opposite, when the game teases for way too long