Injustice
Injustice grips the audience. It makes them so angry, they need to hear what happens next, hoping for restitution, for revenge.
Think of the John Wick series, all built on one incident of injustice: the murder of a puppy. How long can they make movies about this man avenging his dog? As long as the audience is still angry about it.
The Harry Potter series has injustice in almost every chapter. The Dursleys, Snape, Umbridge—Harry flits from one abuser to the next. Meanwhile, his friends betray him, the press lies about him, and Voldemort wants to kill him… Injustice is the fuel that sent J.K. Rowling’s sales to the moon. (That and her wicked sense of humor.)
And oh! Poor Edmund Dantes. The second half of The Count of Monte Cristo is tedious, but I slogged through it—thousands of pages—needing to read about his revenge.
I could mention many more examples—Dickens, The Arabian Nights, Kafka—but you get the point.
In my storytelling, I struggle to create characters the audience will care about. But, really, I’m trying too hard. All the audience needs is a strong injustice—a cheating spouse, a corrupt judge, a bad parent. That’s enough to hook them.