When Harry and Draco are SO OOC that I can't seem get into their characters.
And I agree on the rape. I don't think rape is sexy or romantic.
Where Draco is tortured and humilated by Harry or visa versa.
When I get all into it and I'm thrown a curve ball of self-mutilation and then one/both get turned on by it.
Or when everyone in the fic is gay. It's just not realistic. Unless it's crack.