What’s the worst movie you’ve ever seen ?

Back in the 1970's or 80's I walked out of a French movie, whose title I forget. It was about a car show. The movie alternated between scenes of the cars suck in traffic en route to the show, with lots of horns honking, and scenes of the woman in charge of the show pacing around in an angry panic because the cars were not there. Not much else seemed to be happening.

I could only take so much, and then I left.