Undeserved Misfortune

Undeserved misfortune is when the protagonist gets into a tragic event and nothing can be done about it. It makes the audience feel bad or sad. In the movie Frozen, Anna gets extreme hypothermia until the point that she freezes and she could have been saved if the "prince" loved her. The undeserved misfortune is that she "loved" him and when it came to a life and death matter, she is not granted what the audience wants. 

In real life, there was undeserved misfortune when a guy in my class threw a paper and landed on my teacher's desk and the blame got put on the good student. 

This can combine and be a great idea for a film. We have two best friends who have been friends since they were little. There comes a time where Bob, the bad kid, goes into a store and kills the cashier. They get caught, but when the cops come Bob throws Billy(innocent kid) under the bus and he goes to jail.