Gargoyle. First off, he wears a creepy, expressionless mask all the time. But that's not where he really gets scary, no. He kills people and CHILDREN for no reason whatsoever. He even kills people's pets, these pets can't hurt him or tell people what he's doing, but he kills them anyway just to make the people suffer.
Then there's Gargoyle's death in Episode 39, as the energies of the Blue Water petrify him into a pillar of salt. While it’s a very well-deserved and ironic fate, it’s also still disconcerting to see him petrified alive and for body parts to crumble into salt.
When the American fleet attacks the Nautilus, Captain Nemo has to seal off an engine room of the submarine to keep gas from getting all around the ship and killing everyone. Some men, including Jean's new friend Mr. Fait, are sealed up in the room and will die, but can't be let out because the gas would escape and then everyone on the sub would be killed. All the characters are outside of the door and Jean is very upset and Mr. Fait is comforting him, saying he's accepting his death. Then, quickly after, he's screaming, shouting that he's too young to die, and there's so much he wants to do, all while the rest of the crew, including Jean, can hear him.
Nadia's suicide attempt in episode 35. Although it doubles as a heartbreaking moment, this scene is also psychologically frightening. Over somber, intense music, Nadia tearfully tells Jean that she makes everyone unhappy and will "scatter unhappiness throughout the world someday! If not me, then Gargoyle, or my father... all by using the Blue Water!" After burying her face in her hands for a moment, she looks at Jean and says goodbye. Then she calmly steps toward the edge of the massive tower they're standing on. As she steps off, all sound cuts off. Over silence, we see Nadia fall off the tower, her shadow silhouetted against the light. (Chillingly, the ADV dub has Nadia give off a sigh during her descent, adding a bit of an effect.) After a brief pause of fading to black, we see that Nadia hasn't died at all, but has landed safely on the ground.
The antepenultieme episode, where Gargoyle "tries" Nemo for "accepting to live along humans" with the executionners being his children, Neo and Nadia. Just how much brainwashing was needed to make two children, among them one strong paficist (to the point to consider even self-defense as murder) whose mind was free mere hours earlier, to commit Parricide?
Those wondering how mankind would fare under the rule of Gargoyle should see how he run the island he controls: mass enslavement of the inhabitants, squads routinely operating under no quarter rules, massacres... One can see why Nemo thought destroying Tartessos was the optimal solution.
