Why? Because I had read the Stephen King novella many years earlier, and it was the only story of his that had ever given me nightmares, and I had been dying for it to be made into a movie, and it took 27 years for that movie to finally arrive, and the movie was fantastic for 99% of its length, and then the bloody director changed the ending & completely destroyed what made the story such a fantastic one!!! I have never felt so disappointed at the end of a movie as I did after viewing that one.
The worst movie just for being a really crappy movie? Has to be Sharknado. I know everyone watched it, but a movie where you tip a tankful of sharks into almost every scene (bedrooms, bathrooms, restaurants etc) I found to be a complete waste of my time & I switched it off after about 40 minutes.