I watch a lot of bad movies, and I mean A LOT, so for me to say something is inane/insipid/sucks, it's gotta be a whole 'nother level of crappy.
With that in mind, the worst movie I have EVER seen is a no-budget haunted house flick called "Carnage," released in 1983. Imagine a "Poltergeist" movie if it had been produced for twelve bucks and change with a cast of unknowns.
I suspect that I have a form of film watcher's O.C.D. that DEMANDS that I watch EVERY movie all the way thru to the end, no matter how bad it is. I can count the number of movies I've bailed out on in my life on one hand. Well, "Carnage" tested that O.C.D. to its absolute limit. By the middle of the film I was practically praying that the sweet release of Death would come and end the torture of this movie
Yup, it was THAT bad.
I bought "Carnage" at the dollar store and if it were not for the fact that the director was already long dead by this time, I swear I would've tracked him down and asked for my dollar back.