I'll define "worst movie" as "most failed to live up to expectations". By that definition, I'll have to go with Eragon. Sure, on some absolute scale, there are many, many worse ones, but this is the one that most blatantly offended my sensibilities. It was lazily put together, and just painful to watch. What makes it so bad for me is that I was expecting an easy, simple Heroic Quest with plenty of action. How do you screw that up?