The individuals may not be presented in a positive light and the relationship between the individuals involved may have a bad effect on them, but the sex scene must be presented in an erotic manner.
There may be other sex scenes that are not erotic. Generally sexual farces and horror films are not included.
“Now you're looking for the secret. But you won't find it because of course, you're not really looking. You don't really want to work it out. You want to be fooled.”
― John Cutter, 'The Prestige' (2006)
Great films with poignant, memorable, Shyamalanesque, or downright traumatic endings.
When Movie Twists Fail, via Georg Rockall-Schmidt:
What a Twist: Double Consciousness and M. Night Shyamalan, via Back Row:
6 Huge Movie Plot Twists That Caused Even Bigger Plot Holes, via Cracked:
'mother!’s Ending: What Does It All Mean?, via Vanity Fair:
Why 'The Sixth Sense' Ending Has Never Been Matched, via Esquire:
And the Award for the Grossest Twist Ending of the Year Goes To…, via The Mary Sue: