Twenty Thousand Leagues Under the Sea/Nightmare Fuel


 * While Nemo is a charming, likable man, to the point you can sympathize with him as to why he forsook the world on land, towards the end of the story we get an unfiltered preview of what is underneath it all: a man so insane his rage against the world above has overcome his desire to live apart from them and had led him to become so mad even the men who followed him to forsake the world of Men themselves are reduced to utter terror.
 * It also becomes worse when you realize this is why Nemo occasionally had Arronaux and his friends knocked out while he went on his destructive campaigns: Nemo was conflicted between his remaining humanity and his desire to see all who lives above the waves perish, and over the course of the plot he's slowly losing the battle with himself, but tried to hide this as much as he could until he was too insane to care any longer.