As many film buffs will tell you, the ending to a movie is the most crucial piece. It has the power to make or break an entire film.
A botched ending can sour one's feelings toward an otherwise perfectly fine movie forever.
Remember I Am Legend, when Will Smith's character sacrificed himself to the zombie horde just hours before his companion found the safe zone he'd been searching for the entire movie?

Or Man of Steel, when Superman SNAPPED General Zod's neck to end the final battle in a very out of character moment?

Or Signs, when the family figured out the key to beating the aliens antagonizing Earth the whole movie was simply throwing water at them?
