If someone wants a really good example of the importance of justice in fiction, then Avatar: The Last Airbender did it really well. 

See, audiences are obsessed with justice and fairness in stories. They want the characters they like (the protagonists, usually) to win and for the villain to get their comeuppance. Stories get more complicated and really interesting when they question what justice actually is and what it means for characters to get what they deserve. Should the characters get what they want? Or what they need? If the characters haven’t “earned” it, should they get anything at all? If, at the end of a story, a character has gotten neither what they wanted or what they needed, why not? 

A:TLA covers justice a lot, in many different ways. There’s Hei Bai’s forest, Jet and the Freedom Fighters, Monk Gyatso’s skeleton, Avatar Kyoshi and Conqueror Chin, the Ocean Spirit’s revenge on Zhao, what happened to Katara and Sokka’s mother, Hama of the Southern Water Tribe, Iroh’s past as the Dragon of the West, Zuko’s suffering versus his sins, Iroh and Zuko’s rejection of the Fire Nation’s war and their efforts towards peace, and so on. 

A:TLA’s finale is especially well done because traditional story justice expects Aang to kill Ozai for everything the Fire Nation has done. The characters in the story expect Aang to kill Ozai. It would be long-awaited justice for the world. Ozai is responsible for the deaths and suffering of thousands of people in his time as Fire Lord; it can’t be argued that he doesn’t have a lot coming for him. 

But Aang doesn’t kill Ozai. 

And it still works, because at that point in the story, it’s not about what Ozai deserves, it’s about what Aang deserves. Aang is a 12-year-old boy who has the fate of the world on his shoulders, the last member of a pacifist culture that’s been essentially wiped from the face of the planet, and he doesn’t want to kill anyone. It’s justice for Aang, the last airbender, not to have to kill Ozai.  

Whether or not the audience believes Ozai deserves to die, whether or not the audience believes Ozai’s death was the “right” course of action, they can still at least be somewhat satisfied that Aang is satisfied with this end.