Body mutilation, especially if it's non-con and permanent.
Any kind of stuff where one person is destined to bottom due to biology, such as alpha/omega.
Scat and watersports.
24/7 bdsm relationship in which one person rules over everything in the other one's life, including whether they're allowed to meet friends, go to work, spend their own money etc.
Scenes that are obviously rape but are treated as romantic and in no way messed up within the story, such as the numerous "No, no, please don't do this / Wait, this feels good / I've always loved you" fics.
Characters dropping their personalities on the floor along with their clothes before getting to bed so that I could replace their names with anyone and it would feel the same.
Re: ITT: Backbuttons in smut
Any kind of stuff where one person is destined to bottom due to biology, such as alpha/omega.
Scat and watersports.
24/7 bdsm relationship in which one person rules over everything in the other one's life, including whether they're allowed to meet friends, go to work, spend their own money etc.
Scenes that are obviously rape but are treated as romantic and in no way messed up within the story, such as the numerous "No, no, please don't do this / Wait, this feels good / I've always loved you" fics.
Characters dropping their personalities on the floor along with their clothes before getting to bed so that I could replace their names with anyone and it would feel the same.