Kitanai Kimi ga Ichiban Kawaii !!!!!!!!!! it's truly genuinely Bad Things with Bad End (zero heterosexuality tho don't worry) and at one point in the beginning you might be like "is this just torture porn" but then halfway through there's something that flips and makes it interesting.

WARNINGS IF YOU WANT THEM:
dubcon, abuse (emotional and physical), emeto, watersports, choking, murder/death... there might be a couple i'm missing but this gives you a good idea lol

akuma no riddle is one of my favorites, and it's more "messed up scenario that complicates the relationships" than actually like fucked up, but i still really love it.

i have a couple others on my to-read list that look promising, but i can't actually say how good they are yet:
- kill me now / haegu
- immortal parody
- Destroy It All and Love Me in Hell
- Black Snow. White Moon. Eternal Blossom
- happy sugar life
- love and hate and love (this is an anthology that includes the kitakawa mangaka)

if anyone else has any recs i would LOVE them please