Gesicht arresting people. "I can read you your rights and you can let me arrest you, or you can go unconscious from the gas. Which one will it be?!"
However brief it was, Gesicht forcing the villains into a stalemate. Admit it, you really thought he had a chance to avert Doomed by Canon there for a moment.
Goji visits Professor Ochanomizu, and kills Robot Officer PPB 49881327 "Yuujiro" on his way in, solely to get him to call Atom in for a fight. Ochanomizu refuses, and instead calmly grills Goji on just what exactly is going on, in the process learning that he is probably a lethal threat. Then it turns out that Ochanomizu's only been trying to buy time for a heavily-armed contingent of cops to arrive.
Atom crashing through Professor Ochanomizu's roof to rescue him from Goji. "Let him go!"
Also During his battle with Pluto, says flatly, "I'm going to DESTROY you." Then proceeds to tear off his arm and BOTH horns.
Epsilon knocking down Hercules with his photon energy and then rubbing it in.