Have you ever been to a movie so terrible that you saw people leaving the theater? Which one was it?

Quite a few times, and I've also left a bunch.

We'd have sneak peak movie nights in my local cinema on Wednesday at 10 PM for like 5 bucks, and regular showings would start from Thursday. You never knew which movie you got to see, sometimes it was a blockbuster, sometimes it was bust. That was the appeal of it though.

Occasionally they'd screen some otherwise straight to DVD movie just so that the publisher could advertise with "limited theatrical release" instead. Those were almost universally shit, and most people would leave within the first 10-20 minutes.

Edit: I'm afraid I don't really remember many titles, but one that stuck was Elephant Heart, some family drama about a neglected kid from a troubled family in Germany who was fighting his way out of the "ghetto" by joining a boxing club and turning professional. The dialogues and acting were incredibly terrible.