You could change the ending of Fight Club to match the book but I think that would piss people off.

From what I remember, only one scene of the book didn’t make the film, the narrator and Tyler original meet on a beach. Also, a running theme is that the narrator can’t quite remember how to make home made explosives, he keeps getting the recipe wrong.

So at the end, when they’re going to blow up the credit card headquarters, nothing happens because the explosives are dud.

Sex and the City 2

I’d move the ending to just right before the start so it’s over before it even begins.

Knives is the superior choice to Ramona.

The Mist i think it was called. After the dumb folk pass by the main character in the army truck, a giant alien creature steps on it and kills them all, accidentally.

Us by Jordan Peele. It’s a great movie, but that ending scene is terrible. They don’t need to insist so much to make sure that the dumb viewer gets it… It’s heavily hinted during the last few scenes, and letting the viewer wondering alongside the terrified son who his mother really his, and who we’d like her to be, would be so much more impactfull.

Also Rec by Jaume Balaguerò and Paco Plaza for similar reasons. The movie spends it’s entirerity building this unseen menace, and establishing a terrifying ambiance, and then for some reasons right at the end, just before they let us alone with our thoughts after the movie, decides they should undo it all and give us the “oh actually it’s just this guy who summoned this demon” ending.