Okay, I wish I could join this survivor, but eliminating one movie would be eliminating part of my childhood, I can't, but in the end if Globet Of Fire stills here Imma vote for it
Off: Prisoner of Azkaban (2004) - They failed to explain the most important plot point of PoA... the Marauders.... Goblet of Fire (2005) - They left my favorite part out... the Sphinx in the maze (and turned the maze into something it wasn't...)
Save: Harry Potter and the Half-Blood Prince (2009)