At some point in time we all regret something, but sometimes those regrets hang around and nag at us. If the regret impacts us enough it could end up defining us and our actions. In essence, regrets are dangerous if left unaddressed.

Does your character have any regrets? Will they? How did this regret come to be?

How will the regret affect them? The characters close to or around them?

Will they overcome their regret at some point or will it be their undoing?

One of my characters is kind of a hot head. So in the past she had a bad physical fight with her sister. She regrets that and it helps her keep her cool around her sister from now on. Unfortunately she kind of has a reputation now so all the other characters panic when they think she's about to fight her sister again.