There’s a disturbing trend among many movies and books these days where they focus more on setting up possible sequels rather than telling a complete story. For popular story franchises that audiences have already embraced, this may be fine, but look at the difference between writing a complete story vs. an incomplete one that simply sets up a possible sequel in the future. Complete stories are always more emotionally satisfying so your goal should always be to write complete stories.
A complete story doesn’t necessarily mean the villain dies. In “Star Wars,” Darth Vader is simply defeated in his quest to blow up the Death Star but watching him spin out of control still leaves open the possibility of his return. In “The Hunger Games,” the villain (President Snow) isn’t killed in the end, but he does suffer defeat when the games don’t end with a single winner. Complete stories show the villain failing to achieve his or her goal in the end.
Incomplete stories often leave the villain undefeated. In “Solo,” a new villain suddenly pops up at the end imply a sequel, but this sudden appearance of a new villain means there’s no time for this villain to suffer defeat. Because this villain just appears and nothing happens to him, this story is incomplete and makes the ending to “Solo” open-ended and unsatisfying.
In “Catching Fire,” there’s a cruel commander who takes over the hero’s District and mercilessly beats people up. Yet this villain never suffers defeat. Even though he’s a minor character, he’s left unscathed so this is another example of an incomplete story.
Now in “The Hunger Games,” every villain suffers defeat from the game master who is forced to commit suicide to President Snow whose Hunger Games fails to oppress the nation to the most dangerous tribute who fights them in the end but dies. Complete stories must show every villain suffering defeat.
In “Legally Blonde,” there’s the law professor who just wants the hero as a sex object, but he’s defeated when he hero takes over his case and wins it. The hero’s ex-boyfriend is defeated when the hero does better in law school than he does.
Complete stories are nothing more than every single villain suffering defeat of some kind. Incomplete stories leave villains undefeated and hence create an unsatisfying story. Therefore, strive to always create complete stories. You can find plenty of examples of financially successful incomplete stories (“The Empire Strikes Back”) but when comparing a complete story to an incomplete story, complete stories are far more satisfying every time.