Atonement
Atonement may be all about forgiveness, but that tragic twist ending was totally unforgivable. In the final moments of Atonement, the audience learns that Robbie and Cecilia were never reunited—Robbie was killed during the war and Cecilia died in a bombing. Briony was simply trying to give them the ending they deserved.
Se7en
"What's in the box?" cries Detective Mills (Brad Pitt), only to learn that it contains none of than the severed head of his pregnant wife Tracy (Gwyneth Paltrow). Serial killer John Doe (Kevin Spacey) states that Mills had to pay for the sin of envy; despite the pleas of Somerset (Morgan Freeman), Mills shoots Doe, symbolizing wrath, which in turn completes Doe's meticulous plan.