What makes a story more interesting is that the hero must gradually face the worst fears possible. Initially the hero is trying to solve a problem as painlessly as possible. Then when he or she fails, the hero must keep getting closer and closer to his or her biggest fears to solve the problem.
Consider “Die Hard.” Initially John McClane’s goal is to call the police to alert them to the terrorists. How exciting would the movie have been if he had picked up a phone, called the police, and they showed up to dispatch the terrorists? Boring. What made “Die Hard” exciting was that the hero kept trying to solve the problem of the terrorists until he reached the point where he had to face and kill the terrorist leader himself.
In a much simpler movie, “Grandma,” the hero is a grandmother who has recently lost her lover after a long period of being together. Now she’s just broken up with her new girlfriend when her granddaughter shows up, asking for money to get an abortion. The hero and the granddaughter try to solve this problem of getting enough money through various means, but they never have enough. Finally they have to face their greatest fear, which is to ask the granddaughter’s mother for the money and tell her that it’s for an abortion.
To the granddaughter, that’s her greatest fear that her mother will find out she’s pregnant, but that’s exactly what needs to happen to make the story interesting. Make your hero face his or her greatest fear and that’s what makes Act III so compelling. Act III is the final battle so the hero must face his or her greatest fear.
A movie similar to “Grandma” is “Broken Flowers” where the hero must find and face his past girlfriends to find out which one of them had a son by him. As the hero meets each former girlfriend, things progressively keep getting worse. The first girlfriend is happy to meet him. The second is less happy but courteous. The final girlfriend is outright vindictive.
This gradual descent into hell is what keeps audiences glued to their seats to find out what’s going to happen next. In a movie like “The Matrix,” the hero keeps trying to avoid confronting the villain but when he can’t do that any longer, the final Act III battle pits the hero face to face with the villain in a final battle to the death.
In your own story, keep making your hero confronting increasingly difficult people until he or she finally faces the last person he or she wants to meet. In “Grandma,” that happens to be the hero’s own daughter who doesn’t like her. In “Die Hard,” that happens to be the terrorist leader. In “Beverly Hills Cop,” that happens to be the villain responsible for killing the hero’s partner and friend.
The general motto of every story is that the worst is yet to come. Make life progressively difficult for your hero. The harder life becomes for your hero, the easier it will be to sell your screenplay and make life easier for you.