The Queen's death by Ballister's booby-trapped sword. Ballister holds the sword from the blade, preparing to put it back in the scabbard, and then, suddenly, a ray of green laser bursts from the pommel, which vaporizes the queen. Ambrosius then immediately acts to neutralize the threat by instinctively slicing off Ballister's arm. Both Ballister and Ambrosius look at each other with shock, and Ambrosius' expression makes it clear that his action was not completely deliberate.
How utterly casual the Director is when stabbing (who she think is) Ambrosius after revealing she was the mastermind behind the Queen's death. While it turns out Nimona is unharmed, the real Ambrosius bursts in a moment later... Which implies that might have been his fate if he had expressed his suspicions to the Director.
The Reveal of the truth behind Gloreth's Creation Myth. A thousand years ago, Nimona was best friends with a young human girl named Gloreth. But when her parents saw Nimona shapeshifting, they called her a monster and the people of the village tried to kill her with torches even as she tried to run away from them, leading to the village being set on fire. Finally, after being pressured by her parents, even Gloreth turned against Nimona, pointing a wooden sword at her and saying, "Go back to the shadows from whence you came."
After Ballister rejects Nimona, she flies past the Despair Event Horizon and decides to become the monster everyone sees her as, transforming into a gigantic pitch-black creature that resembles a Living Shadow with numerous glowing white eyes, big enough to destroy the whole city. It is so unlike her other cutesy and pink-colored transformations that it is less of an animal and more of an Eldritch Abomination. None of the Institute knights' attempts to attack it even succeed at scratching it. The scariest (but also saddest) part is that you can hear Nimona's anguished screams in its roars.
When Nimona's monster form is on screen, the lighting of the scene sometimes distorts and flickers red and blue, as though the viewer is watching through a damaged camera, or her presence is affecting the film itself.
