Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: Alphas
Stanton Parish suffocates his dying granddaughter in her bed, presumably to end her suffering. The fact stands that he's willing to murder his own flesh and blood.
The episode Gaslight. Flickering lights, dark hallways and vivid hallucinations.
Nina's usage of her power when she's not on the straight and narrow. While her usual usage is hardily "good" when she's snapped she's downright evil. Look at her actions during "When Push Comes To Shove":
Forces her childhood sweetheart to leave his wife and kids to stay with her note It should be noted that she didn't seem to realize she had done this one at the time, not that it makes it any better.
Forces Rachel to kiss her knowing exactly how Rachel would react to such a thing with her powers
Casually commands a waiter to go and get a certain condiment knowing that he'd jump in the sea to get it - and laughing almost manically at it
Making Hicks shoot anyone who attempts to stop them. Somebody who should know better than anyone how Hicks felt after Ghost used him.
This was made worse the fact of how deadly efficient Hicks is when pushed.
While captured, Scipio (Who's ability is to light fires when full of adrenaline), taunts Dr. Rosen about his daughter. It should be noted that Scipio's left hand is right over his heart, in case he attempted to break out. Rosen calmly explains that he's going to inject Scipio full of adrenaline, simulating the experience all of Scipio's victims (which include his parents and sister), which, in Scipio's own words, is "Making their skin sizzle." Scipio's screams while he burns himself are horrifying, and fully show what Rosen is capable of.
Parish's "self-made armageddon" is a very disturbing concept that embodies the term Paranoia Fuel: There you are, living your life, when a sudden light flash causes your brain to break down and you spend the last seconds of your life debating like a squirming fish as you lose consciousness. It may be quick and painless, but damn Parish, that's some horro movie level stuff you've got there.
Also take note that when you're being restrained and you see Kimi Milard walking towards you ... unless someone saves you, you're freaking screwed!