I talk a lot about the importance of endings and beginnings. In fact, I’d argue that the first thing to determine before outlining your screenplay is to KNOW YOUR ENDING.
We’ve all been there, enjoying a great cinematic ride, only to have it destroyed with a painfully forced and unbelievable end. When writing a screenplay, the ending is key, and it’s wise to allow the ending to dictate how you begin. However, you must also be flexible. As the story takes shape, it’s a mistake to blindly stay the course, especially since not all stories should end “Happily Ever After”.
Happy endings are for rom-coms and storybook princesses, but film endings can be tragic, bitter sweet, even depressing. The key is an ending that’s satisfactory. Imagine Braveheart with William Wallace NOT being tortured and martyred in London Square; instead, all his Scottish mates hiding in the crowd come rushing out to rescue him. The ending now would be trite and unbelievable, with the theme of freedom through sacrifice becoming insignificant.
You must be honest with your story and in tune with your audience. Was Indiana Jones and the Kingdom of the Crystal Skull really satisfactory when the Mayan temple turned out to be a spaceship? The simple truth is that your audience will forgive flaws in the beginning or middle of a film, but an unsatisfactory ending is unacceptable.