There’s literally only one movie I’ve never finished because it was so shitty.
It’s a film from 1989 called Things, a low-budget mash-up of Evil Dead and Alien, shot on videotape in Canada at the estimated cost of 30,000 CAD (which, considering the end result, seems about 30 times more expensive than I would have guessed). I have watched bad movies on purpose since I was 10 years old, and I shut this off halfway through.
If you’re a stronger man than I, it’s available for free on Amazon Prime right now, but you can’t say I didn’t warn you. On the flip side, not only have I finished many of the movies that follow, I’ve seen a couple in theaters more than once. As I said, I love watching bad movies.