This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Kingdom Hearts coded
Sora's Heartless is somewhat disturbing, considering how nice Sora himself is.
The data version of Castle Oblivion is in some ways even more disconcerting than it was in its original form, because the illusions don't actually work on Data-Sora, resulting in a jarring disconnect between what its inhabitants are saying and what he actually sees.
Several of the world endings in Castle Oblivion imply the death of either Data-Sora or an NPC. This is the normal ending for Wonderland.
In Agrabah, Jafar gets a hold of a glitch-created copy of Genie's lamp, and promptly uses it to freeze time. Data-Sora then has to race against time in a monochrome-green, almost completely silent Agrabah, whilst dodging harmful apparitions of Jafar.
At several points in Wonderland, the glitches cause the card soldiers to freeze in place, multiply, or run really fast, and while the non-glitched cards will yell at Sora if they catch him, the glitched cards make the text-only equivalent of groans of pain. At one point, Sora's path is blocked by an army of twitching cards with raised axes.
In the HD remake in Hollow Bastion when Data-Sora is Keyblade-less, he, Donald and Goofy (who have shown up to help him fight) confront Pete who ends up trapping Donald and Goofy in Bug Blox meant for Sora; he attempts to kill them and almost succeeds by crushing them in the Blox.