I love a bad ending in which my love interest is impregnated by another guy before I confessed to her (maybe I went somewhere and left her with him, or maybe he got her before I even knew her). Knowing she's been tainted and filled by someone else, and taught about sex, before I could do it is extremely hot to me. It's difficult for me to reach orgasm with any other thought. The game over/mission failed endings are always my favourite.