Carl's moment of white rage in the throne room and the deliberate step back from becoming what he hunts.
Standing over the marked, half-dead Empress D'Nadia, Carl is hit by a rage so brilliantly white that all three of his eyes burn. He compares it to everything before — Maggie My, Quan Ch, the gas station with the button that would end it all — and finds it worse, because unlike the warlords and the hunters and the Prince Maestro, she concealed what she was and pretended to be one of the good ones. A voice whispers that it's so loud, and Carl tells it to be quiet.
He messages Princess Donut that he's changed his mind and wants to do it himself. Donut refuses outright, begging him to step back and promising she's got it. And then Carl sees the edge, clear as can be, standing on it with one foot stretched out over open air — the observation that clarity comes when you need it most — and he takes a step back, telling Donut it's time.
Carl's near-fall into personal vengeance, and the choice that keeps him from it.