The main reason the final Act of every screenplay must be the most exciting part of the entire story is because this is where we get to see who wins in the end. If the hero wins, then the villain loses. If the villain wins, then the hero loses. This must be clear cut so we’ll watch the inevitable conclusion to see who wins and how.
This is why every good movie makes this conflict clear and inevitable. For the hero to win, the villain must lose. This means the villain must fight like crazy to win, which means the hero could lose. There can only be one winner and that’s what makes an emotionally satisfying conclusion. More importantly, this conclusion must be final in the sense that once someone wins, the other person has clearly lost.
Think of every great movie you’ve seen. In “The Hunger Games,” the hero (Katniss) either wins by surviving or loses by dying. If she survives, she indirectly defeats the President (the villain). If she dies, then the villain wins.
In “Eddie the Eagle,” the hero wins by competing in the Olympics while the villain wins by keeping the hero out of the Olympics. In “10 Cloverfield Lane,” the hero wins by escaping from the underground shelter while the villain wins by keeping the hero locked inside the underground shelter.
Bad movies foul up the ending in two ways. First, the conflict between the hero and the villain isn’t conclusive or inevitable. Second, the conflict is conclusive and inevitable but there’s no emotional satisfaction in seeing the hero win and the villain lose.
An inconclusive conflict is the easiest problem to spot. In “The 5th Wave,” the hero’s goal is to rescue her little brother, but the villain’s goal is to wipe out the human race. This should be an inevitable conflict because if the hero wins, the human race won’t be wiped out completely and if the villain wins, the little brother will die.
Yet in the actual movie, this doesn’t happen. The younger brother is in no threat of dying. He’s simply being herded into a military transport and sent to another military base that’s run by the aliens. If the villain wins, the younger brother will still be alive so the ending isn’t conclusive. If the hero wins by rescuing her little brother, then it has no effect on the villain whatsoever since the villain’s overall plan to destroy the human race can still continue.
Thus the ending is not conclusive and that’s what makes the ending so emotionally empty.
In “Star Wars,” either Darth Vader wins by blowing up the rebel base and killing Princess Leia, or Luke wins by blowing up the Death Star. Once Luke blows up the Death Star, there’s no way Darth Vader can destroy the rebel base. Once Darth Vader blows up the rebel base, there’s no way Luke can save the rebel base or Princess Leia. It’s an either-or conclusion.
Yet in “The 5th Wave,” there’s no conclusive ending. A better ending would have allowed the villain to kill the younger brother or the hero wrecking the villain’s plans. Neither happens so the ending is emotionally unsatisfying.
Endings must be simple to understand. In “Deadpool,” the hero (Deadpool) wants to kill the man who tortured and created him. The villain wants to kill the woman the hero loves and kill the hero. If Deadpool wins, the villain loses. If the villain wins, Deadpool (and his girlfriend) lose. It’s clear cut and definitive in the end.
Sports movies are often easiest to identify with their endings because in sports, there’s always two teams and only one can be the winner. In “Rocky,” either the hero wins or the villain wins. Both can’t win. yet in “The 5th Wave,” the villain doesn’t really lose just because he no longer has the hero’s younger brother, and the hero doesn’t really defeat the villain just by rescuing her younger brother. Essentially the hero and villain have no purpose or conflict with each other so that weakens the conflict even further.
Conflict must be inevitable and conclusive. Study bad movies and you’ll often find the ending muddled. Study good movies and you’ll always see an inevitable and conclusive ending that leaves no doubt who won in the end and who’s conclusively defeated.