I’m struggling to think of the worst film/s I’ve ever seen, although there are a lot of films that I can’t say I’ve particularly enjoyed or would want to see again. Many of the films mentioned in this thread are ones that I’ve liked.
What I do hate is when sequels are churned out if the original film has been successful, e.g. the Jurassic Park franchise. And many re-makes are pretty bad, e.g. the last Little Women.