This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Promethean: The Created
The Zeka from Promethean: The Created. All Prometheans have things really bad, but Zeka are a whole different story. For starters, they are in constant pain. That's all there is to it, they just have to live with the pain. Unlike normal Prometheans which can heal from electricity, Zeka need to be exposed to huge doses of radiation. They have some of the worst Torment and Disquiet affects, causing hysteric fear where they go and becoming Omnicidal Maniacs when overcome by Torment. No prize for guessing what theirWasteland looks like. When you take all of this into account, it's no wonder that not a single one has completed the Pilgrimage, and that it's ridiculously easy for them to become the aforementioned Centimani. The worst part?Their numbers are growing.
It says volumes about Promethean that it getsworse. If Zeka do achieve their Pilgrimage, they immediately take a potentially lethal hit of radiation (intensity is equal to their Azoth, which kinda sucks if they have Azoth of 5 or above — five-dot radiation is automatically lethal, and to have even a decent chance at the New Dawn, 5 is the lowest Azoth you can have). It generally goes "Yay, I managed to become human! Fuck, is that thing my intestine? Aaaargh." *DIES*
In fact, there's an In-Universe theory that a Zeka can't reach the New Dawn the way other Prometheans do — that if they try, what happens isn't a transformation, but an explosion. Exactly what of is anyone's guess; "best case scenario" would be nuclear radiation, worst case... pure Flux.
Of the Zeka, the two worst are Oleg Wormwood (a Manipulative Bastard and Omnicidal Maniac who is this close to achieving his goal of Nuke 'emAll), and Tsar Bomba, a maddened, delusional sadist, who believes it is his destiny to rule a nuclear wasteland.
The sourcebook with the Zeka in it also applied this to Pandorans. Not from the perspective of Prometheans, although this is entirely the case. No, being a Pandoran or Sublimatus. You have a ceaseless hunger for Promethean flesh; you petrify on contact with humans; you have a number of instinctive sadisms; and, to make matters worse, you're doomed to spend the rest of your existence as a monstrous undead thing devoid of hope. Unlike Prometheans, you can't be cured.
The lacuna, a ritual used to steal vitriol from other Prometheans. The process is deliberately described with a rape-like subtext, but is in some ways more evil than sexual assault: by performing the lacuna, you are deliberately sabotaging another Promethean's Pilgrimage for your own personal gain. No surprise that it always causes a Humanity drop, not unlike diablerie.
It's hard to say what's worse: the possibility of becoming the victim of a lacuna, or getting so desperate that you would perform the lacuna.
Disquiet: the more time you spend around non-Prometheans, the more obsessed they become with you, until they try to kill you or capture you. At its highest level of Disquiet, it becomes infectious.
The fourth level of Disquiet can only be cured by murdering the Promethean who caused it (and making sure they stay dead). Imagine what this means for those who reach this level and can't destroy the Promethean. Towns torn apart by petty rivalries, where no one will speak a word to their neighbors that aren't insults; places where strangers are likely to be kidnapped and interrogated about "the strange man;" cities where a handful of demagogues preach the Red Scare while the masses cower at the feet of their lecterns. All because one poor bastard just wants to be free of humanity's hate and got out before the Torches and Pitchforks could find them.
Think about the fourth level of disquiet from the perspective of a human. Some inhuman monster decides to try to settle in your little town, even though he knows that it will drive people insane and kill the land. Even as the madness starts to affect multiple people, the monster still stays, even as their land starts to dry, fires spread, and electronics bust and become useless. People begin to form cliques, becoming obsessed with one upping everybody else. It escalates to the point of violence, until someone remembers the stranger who started it all. So the monster leaves, even though it knows it's driven them all irreparably insane, to save its own skin.
Imagine living in a Wasteland: For no explicable reason, things start to go wrong. Electronics go haywire, the water becomes undrinkable, words stop having meaning...
Any time a Promethean uses pyros, it causes a small Glamour Failure that reveals their often gruesome disfigurements. While that doesn't sound too awful, just imagine talking to someone when they suddenly, just for a moment, look like a living doll or a desiccated corpse. It'd be like a real-life Screamer Prank.