Barney has always been a little creepy, but after reading thisDark Fic, you'll never think of him the same way ever again.
The wrestling fic Mind Tricks...where it's revealed that everything that's happened was just pure randomness. There was no reason for all the pain and torture that the characters have all been through but that Rey Mysterio's name popped up from a random number generator created by the government from the census and other methods of data collection, because a scientist was a little too devoted to the idea of the scientific method. And he's only one of thousands of people with the same fate. And the story regularly makes you realize that no, it's really not as absurd as it sounds, because it's pointed out regularly that there are real-life, moderately famous cases of the government screwing with people in ways just as terrible. And not only all of that, but you might not be able to be sure if any lost loved ones of yours might not be dead, but rather somewhere being tortured horribly in the name of national security. Good luck ever feeling safe again.
Odd scout. All three chapters. Now, just remember that he's BEHIND YOU RIGHT NOW.
Luminosity. Chelsea's power was scary enough on its own, what with the cutting/enhancing relationships. Then, in the Villager chapter of Radiance, it happens to the first-person narrator. Oh, and by the way? No, it doesn't feel like she's doing anything but smiling and making small talk.
Chelsea doesn't affect moods directly.\\She doesn't have to.
Strung Up, a Space Channel 5 dark fic in which Purge is trapped in a nightmare and is made into a living puppet as strings are stabbed into his body and he's forced to move to see his friends/robots destroyed. The scariest part of this fic? Entity could haunt you in your nightmares, and force you to go through those things at anytime he wanted. Enjoy sleeping tonight.
In-Universe in "The Time Pauser": Calvin is extremely defensive about his new invention, going to great lengths to protect himself from those supposedly watching. Possibly justified, as said invention could possibly be devastating.
Another In-Universe instance in "The Case of the Rogue Water Balloon": Hobbes is extremely unnerved by Socrates' security camera in his room. (He ends up trashing it.)
Hivefled: the Torture Porn prequel, Reprise, involves a slow and careful build-up before the actual Rape as Drama appears. One reviewer described it thus; "I was reading and thinking 'Well, this isn't so bad, a little creepy maybe, but I think even I wouldn't do too badly in an environment like... uh... oh... oh dear God.'" Then it becomes clear that the Big Bad couple have groomed, captured, tortured, and killed nearly two and a half thousand teenagers over the millennia, the youngest of whom who survived long enough to have his soul bound (implying younger ones were also tested) is the equivalent of a human twelve-year-old, nobody is aware this is going on, and it's likely a significant proportion of troll society would applaud it if they did know.