Why your protagonist and antagonist share the same flaw

Your protagonist and antagonist aren't opposites. Both start with the same flaw and split over one decision.

Name one good quality and one bad one, and it looks like you have a good side and a bad side. You don't. The bad one is what StoryDNA calls your story's Vice: the destructive quality your story argues against. It shows up in your protagonist first.

It comes out through your protagonist's own weakness, before they're even aware of it. Being on the right side of the argument doesn't protect anyone. They take the same shortcuts, reach for the same comforts, trust the same false securities.

So what splits them isn't their nature. It's two responses to the same pain. Your protagonist keeps choosing the costly thing with their eyes open. Your antagonist decided the pain wasn't worth facing.

Michael Corleone in The Godfather doesn't start outside his family's violence. He starts as the one family member who has turned it down. The film is him slowly accepting a way of life that was in the room the whole time.

Two people can carry the same pain and end up enemies. What separates them isn't character. It's whether they kept paying for the decent thing or found a way to stop.

So name your protagonist's weakness, then check that it's a version of your story's Vice. If it's a different flaw, your theme and your protagonist's arc are two separate stories sharing a title.