One thing happens that makes them realise they could be wrong about something or someone, another thing occurs to confirm that feeling and so on. I love it even more when the character tries to resist the change that is inevitably coming. Will they hold out? What will make them break? Assuming they do break and do change, do they regret holding out for so long?
So what would your characters need to repent of? This doesn’t necessarily need to be crime based though that is one logical way to go. What brings it home to them they have been wrong? How do other characters react when they change? Are they convinced by the new behaviour or not? Do they feel threatened by the change in the character and, if so, what do they do about it?
Change has consequences, so this must be reflected in your characters too. Staying still and/or not facing up to the need to change also has consequences. Which way will your character jump? You can have lots of fun writing out these possibilities and working out which is best for your story and character.