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Nightmare Fuel: Empowered
Y'know, for a book that began as a spoof on BDSM manga, Empowered has gotten pretty goddamned grim.
Knight of Cerebus Willy Pete wants revenge on Thug Boy for ripping him off. How? Well, the rest of the Witless Minions were used to satisfy the physical lusts of a man who is walking flame. And because the normal orifices don't last long enough to finish the job because they burn too quickly... he has a thing for eyes. There's a reason Willy Pete has pride of place in Thug Boy's nightmares. He's since added eating bits of living people to his repertoire, and frequently alternates between eating and sodomizing his victims in order to prolong their suffering for as long as possible.
Mindf██k's backstory has a fair bit of this. It seems her rather psychotic brother had similar mental powers and used them to take over her motor functions in order to induce the whole Disability Superpower thing by forcing her to carve out her own eyes and tongue with a rusty pair of kitchen shears. Please note that Mindfuck was both conscious the whole time and well aware her brother thought he was doing her a favor.
And if that wasn't enough, Volume 8 shows that, courtesy of Mindf██k's additional Power Incontinence while asleep, Spooky (and by extension, the reader) saw this very moment, as Mindf██k has a nightmare over it.)
It gets better. See, Mindf██k's brother manifested his powers pretty early, so much so that the constant assault from the people around him traumatized him. He got over it when he discovered that he could edit himself, meaning his personality, thought patterns, etc. But, he kept on editing and tweaking himself until he was a teenage boy with no fear, no doubt and thus, as Mindf██k puts it, "no consideration as to what he may be doing is wrong." That's nightmarish in and of itself. Now consider that he believed that making Mindf██k cut out her eyes and tongue were the absolutely right things to do, because it would make her a better telepath, and doesn't help that his pre-editing self perceived her sister to be a monster. It doesn't stop there, either (oh God, I wish it did.) Mindf██k, partly in retaliation, edited herself after the event to be who she was when we saw her - she outright says that she doesn't know if the end result is her at all, and spent her life wondering if she was a monster like her brother thought before she edited herself.
And then, there's what Ninjette's ex-clan had planned for her (multiple amputations and a lifetime of rape) - and what happens to the assassins they send to collect her.
The fate of Ninjette's first boyfriend. There's not enough Brain Bleach to fully describe her father's method of torture and murder.
Ninjette's story of how she lost her virginity ends with her drunk father covered in blood standing over her carrying her lover's head stuffed with the kid's own genitals. Her father mentions he slaughtered the boy's clan members to get to him and that they're currently at war against their closest allies. A war which Ninjette won't be participating due to not being able to walk, eat solid food or piss without blood after he's done with her. To make matters even worse he tells her to take a good look at her first kill, stating it's her fault he had to kill the kid.
The Super Dead (don't-call-them-zombies), especially when you consider that this could potentially be the fate of half the characters. Most of them are fully conscious, and their bodies are rotting in front of them.
As if that's not bad enough, once they fall into the clutches of DeathMonger who installs his necro-puppet-ware in them, they're fully conscious with their bodies rotting in front of them andforced to do his bidding like living... erm, un-living puppets. So much to look forward to.
And if Spooky's infernal service provider happens to be telling her the truth about what happened to Mindf██k... poor, poor Mindf██k. Adam Warren likes his woobies extra-broken, but it's depressing how many horrible things have happened to (arguably) the sweetest girl in the series.
Mayfly. Spooky spells out that hundreds of people have died horrible deaths as a result of the mutagenic substance, and it's likely we're talking people's entire body exploding with cancer.
One of Emp's first times out as a cape and being buried alive and almost drowning in her own snot.
Even worse, there is some implication that she DID die and is an unknowing Superdead.
Book 8 has, among other things, Spooky being embraced and dragged down by dozens of burning Mind***s, and the terrifying flashback of Mind***'s mutilations. It's NOPE on an entirely new level.
Also from Book 8, the end of the fight at San Antonio: after the initial attack from Thugboy and his friends, dozens of Capes and Villains had started an all-out fight when the leaders of the heroes decided to use an alien superweapon codenamed 'Vorpal Sword' (an aircraft-sized sword-looking submunition drone with enormous penetration abilities they had used for about ten years for shock and awe), and lost control of it. The end result was a supervolcano, and the barely-avoided destruction of the whole American continent.
Willy Pete, as mentioned above, is highest-order nightmare fuel already, but consider this for a moment: A normally vague divination gives Spooky not a general idea of where Willy Pete can be found, but a precise where-when, down to and including GPS coordinates. Spooky's mystical powers are of entirely infernal origin, meaning that the very powers of Hell itself want him destroyed!