What Is The Worst Change A Film Adaptation Has Ever Made?

Movie adaptations always require a few changes from their source material. Sometimes those changes can result in a totally new and wonderful experience—and sometimes they're just plain terrible. Which alteration is the very worst?

Include the title of the film (and the source material, if it has a different title), the change the filmmakers made, and why it was terrible.

The top image is from The Last Airbender, M. Night Shyamalan's disastrous adaptation of Avatar: The Last Airbender. Let's face it, this movie had a lot of problems, but changing most of the Asian-influenced characters to white kids wasn't a great place to start.