Im looking for a novel where the parent realize their at fault completly and try to atone(with actions) like death the only ending for the villian.
The third trilogy of Sheri S. Tepper's "True Game" series (3 trilogies, so 9 books total): https://www.amazon.com/End-Game-Footseer-Daughter-Star-eye/dp/B0013OX6Z8/ Note: the MC is not the parent at fault, but she does finally convince the actual parent to deal with their kid who was screwing up the world.
Damn it man. I can accept magic and fantastic creatures. But parents realized they're the ones at fault? Now that's totally unrealistic.