Fate/stay night/Nightmare Fuel

Ah, Fate/stay night (and by extension Fate/Zero). Kinoko Nasu comes close to H.P. Lovecraft in creating both Humanoid Abominations and Body Horror in his settings. The bad endings that you can get range from depressing and squicky to pure, undiluted Nightmare Fuel. Have fun sitting through forty bad endings to get Hundred-Percent Completion...

"Once swarmed by these lust worms, men will have their spine crushed, brain sucked, and will be made into a cripple. The worms will transform when attacking a woman, so that they are only able to violate . Unwilling to eat human flesh, the worms have only one way to get what they desire. As a result, the woman's mind and body are completely violated and destroyed."
 * A lot of the game overs are like this. You have no idea what a violent, meaningless death is until you've played this game.
 * And then there's Heaven's Feel. One shouldn't play it at night. As a whole, it is like the End of Evangelion of Fate/stay night, plenty of Tear Jerkers with most of them made of Nightmare Fuel. From 's Backstory, Start of Darkness, the Bad Endings, a massive, everything in between, AND a  Good luck to NOT Go Mad From the Revelation.
 * Whatever you do, don't think about the Makiri parasitic worms. Don't think about how, if you've had the comparative good fortune to be born male, they'll simply kill and eat you. And especially don't think about how, if you're unlucky enough to be female, . Even more, don't think about how  And this is JUST the backstory!
 * Not to mention that these worms are PENISES with More Teeth Than the Osmond Family.
 * You know, the game itself says it best. Death by Sex, indeed:


 * Then there's the final bad ending you can get.
 * Fate, Day 15 Church Basement.
 * Notable bad ends include any that involve Ilya, and the one where Caster turns Emiya into a living wand for projection magic and Rin ends up mercy-killing him. However, the most scary one was the completely out of nowhere bad ending (caused by just asking too much about Caster) where Issei, under Caster's control, stabs Emiya and then slits his own throat.
 * There's also the one where Kuzuki punches Rin's head off and blows a hole in Shirou's stomach.
 * The ones where the player's view fizzles out like a broken TV with appropriate sound effects.
 * the first Game Over you can get: simply put, you're reduced to a head and torso by Illya's Servant, cursed by Illya so that you can't die or lose consciousness unless your head is destroyed, and then taken captive to be tortured by her for eternity. And all because you choose not to be Saber's Master. Well, so much for free will.
 * You can't fight Fate/stay night?
 * It happens because you don't have Saber to defend you, but as Ilya cheerfully explains, she really just felt like doing it. The fact that Shiro is being reduced to a disembodied head doomed to eternal suffering for what is, essentially, Ilya's vague whim just makes it a million times worse for me...
 * Zouken. Matou. Most specifically, the scene where he sends worms after the drunk woman who has no idea what is going on while they devour her alive, and all the while there are these chewing noises.
 * For more Fridge Horror,
 * Except, Taiga is alive in Heaven's Feel True End. The " " part might just be Rule of Fun.
 * Most of the Nightmare Fuel in this series comes from the sheer amount of Body Horror inflicted on people. For example, we have Smug Snake Shinji Matou getting horribly transformed into a living mass of flesh that's barely conscious, eventually becoming a vessel for The Corruption...
 * The worst Body Horror?  "I am the bone of my sword" indeed.
 * Assassin is creepy.
 * Kotomine's ending in Fate/unlimited codes. He . It even plays All The World's Evil instead of one of the standard ending themes during the credits!
 * It's a real tribute to the writing that quite possibly the most chilling Bad Ending in the whole game is the "Superhero" ending on the ninth day of Heavens Feel, which involves neither a gruesome and horrific death nor an And I Must Scream scenario. You reach that ending by choosing to, and the last words are: "There's no need to talk about the obvious outcome. Emiya Shirou will turn his mind to steel, and become a superhero." The implications are... unsettling.