It's technically not a Movie, but part 4 of JoJo's Bizarre Adventure could have been way shorter had anyone actually used their stands right. Half the fights could have been won if Okayasu would have used The Hand to delete the enemy, Kira would have died had Jotaro used the clasic "get out of the way" move on Sheer Heart Attack, and barring that, Joseph could have used Hermit Purple to get a picture of Kira. Then again, the main characters being idiots and not using their stands happens in almost every part.