Avengers: Infinity War

The third act turns on a character being an idiot. That story beat renders all that the heroes do before and after it immaterial. That moment so preoccupied me that I couldn't enjoy the rest of the story, and made it impossible to ignore the flick's other glaring flaws anymore: the villain's motive makes no sense, the glove exists only to produce plot contrivances, the score is so obvious it might as well be cue cards on screen ("Feel sad now") ... The first half is some of the best action in a Disney Marvel entry yet, and the other half is so stupid that it sours the whole MCU experience.