First thought is that its almost certainly something from Warhammer 40k. Probably one of the Dark Eldar (or just their civilization as a whole). They're a super-advanced, post-scarcity civilization that basically worships torture and uses their technology to "perfect" it.
Na, the C'Tan is the cruelest. You Necrons want to be free of cancer riddles bodies we caused by consuming your sun and become immortality? Sure, here is a metal container for your brain while we consume your essence because it taste better than solar winds.
There was an old Captain America comic where the Red Skull had a glass floor in his dining room so he could look down on the torture chamber underneath.
Not only do they see all the horror and suffering that Anubis and the goa’uld inflicted on the universe; the could have done anything… not even helping; rather they never even hindered Anubis
They didnt do shit until he halfway ascended and became a threat to them. And how did he halfway ascend? Oma fucking Desala meddled with the mortals, again. And when a mortal gave up everlasting life and power to un-fuck their mistake, they un-ascended him!
They really took a nosedive in the public relations there.
The Crippled God from Mazalan Book of the Fallen. I should probably spoiler this. And trigger warning.
spoiler
The High King Kallor once ruled an empire. And he did so with a cold hard iron fist. Some Elder Gods decided that he was to be dethroned, and set off to confront the High King. Kallor had gotten wind of this before the confrontation and so had all his mages begin a ritual. One that would summon an alien force from beyond the known universe. They were successful and pulled an entity of such power that it destroyed Kallor's entire empire. As the Gods approached the High Kings throne they found him there, emporer of only ash.
The power Kallor summoned was so alien and anthemic to the universe it needed to be destroyed. But they found it couldn't be done. So instead they crippled and chained the power. This power came to be know as the Crippled God.
It's hard to pinpoint exactly the cruelty that the Crippled God did himself. See, the crippled god worked in the shadows from his tent on the beach. He lifted others up to enact his broken visions. Granted them slivers of his alien power, and whispered promises of power or revenge into their ears. One such figure was the Pannion Seer.
The Seer was a holy figure who led an massive army, the Pannion Domin, on a crusade against the world. This was a holy war and such his followers where blindly devoted. His most devoted where called Tenescowri. The Tenescowri where purposely starved. Given no rations, no water, no food. They had to subsist on what they were able to find. And what is the most common thing found after a battle? Dead bodies. The Tenescowri was an army of forced cannibalism.
It gets a bit darker. The most powerful of the Tenescowri where the Children of the Dead Seed. During battle the fervent women would take dying men, and force them to copulate. Filling their wombs with the seed of a dead man. These children would grow up to be unholy warriors.
I think it was said the Tenescowri were 100,000 strong led by Anaster the Fist Born of the Dead Seed.
How is this series? I only glanced at the spoiler but some of the last bit was...a lot. Do most of the books receive that trigger warning or is that more of a endgame thing?
As Llamapacolypse said, it has it's dark moments. What I wrote above is some of the darkest. It never goes into too much detail when it involves some of the more triggering things. Just a fade to black.
That said it's such an intensely human series. So much love and compassion litered throughout the whole thing.
It's also such a unique experience. Most fantasy books have huge massive reveals that shock and take you by surprise. Malazan has these things. But it also does it in reverse. You'll read something and then a book or two later it changes context entirely, completely blowing your mind.
The series is fantastic but it does get quite heavy in a lot of ways. Very heavy on the ways people and societies are shitty to each other, but the central theme of it really is compassion.
Causes the Necrons to be a short lived race because the C'Tan living in their sun. A series of wars happen and the C'Tan is like "oh hi, we can make you 'immortal'"
Turns the civilisation of Necrons into the slave machine race we know in 40K
The worst part was, the C'tan which ended up being known as The Deceiver convinced them that they could make the Necrontyr immortal, fixing their cancer ridden short lives, and aid them in their war against the Old ones. This was accomplished by a process called bio-transference using the bio furnaces. As the Necrontyr either willingly or unwillingly lined up to burn up their bodes in the furnaces, the C'tan could be seen above the bio furnaces gorging on the souls of the Necrontyr burning.
This is a very interesting thought: the Dowdy alien you mention has wiped out an entire race of 50 billion beings, but is aware of his crime and lives in self exile. He's committed an atrocious crime in a rage fit.
On the other hand, the changelings committed a planned crime with intent to cause suffering.
I'm not sure who's worse: the Dowd by magnitude of the crime, but the Changelings ruthlessly command their Dominion.
I dont remember the name of the episode, but Bashir took a leave of absence and hung out on this planet for, I'd guess, a year to work on a cure. He didn't find a cure but managed (by accident) to make a vaccine that saved new-borns from getting infected.
The Fleshmancer in Sea of Stars is pretty terrible. He creates giant, potentially world destroying, monsters that feed on different types of despair, and so seek to create those emotions in as many people as possible. He committed one genocide against an entire race, and then trapped them in living death, unable to be seen, or leave his lab. He seems to have committed another genocide, just to make a birthday present for his friend. And this is all on just two planets, when he is acting in the same way across the entire multiverse
I don't remember all that much about Inuyasha but I remember while watching it thinking I had never hated a villain so much in any other thing I'd seen
It was even more insidious than that. It wasn't about self-preservation or selfish need... they were so brainwashed they considered it good to tell on others as a matter of course. One of the secondary characters is even proud of his own children for turning him in for talking in his sleep.
Semirhage from the Wheel of Time. She was a torture specialist who would use the one power and her knowledge as a top healer of the body and mind to use both pain and pleasure to turn her victims to the dark or send them to attack their loved ones. She was effective enough that they tended to either succeed or fail because they were found out, rather than the person deciding against it once they were free. Even those who had turned and were restored using age of Legends mind restoration techniques lived in constant fear of ever being in her hands again. They had to take special precautions to prevent prisoners from committing suicide after finding out they were being put in her charge. She was a sadist who would cause unnecessary levels of pain during her healing even before the bore was drilled and joined the dark because she was caught and offered the choice of oath rod vs violence or being severed from the source.
Though some of the other Forsaken give her a run for her money.
Graendal with her mind slaves that she would use for pleasure or just furniture.
Sammael who, when told that he was giving his prisoners of war half the food they needed to survive, immediately ordered half to be executed (and generally just fed them to the trollocs even when they had enough food).
Aginor who joined the shadow because they wouldn't let him do the experimentation on animals and people that he wanted to. He then created the trollocs and other shadowspawn and took 10k people per day for experiments and fodder from the start of the war power to the end of it, potentially doubling that number in the last 5 years of it.
Moghedian who ran evil schools that had children at first informing on their loved ones and later carrying out their executions themselves. During the breaking of the world, these children caused chaos that seemed like they were racing against male channellers going mad to break the world.
Balthamel established breeding camps for humans to be fed to trollocs. He also had a temper that almost got him oath rodded before the war of power.
Plus just general genocide, terror, manipulation, war, and oppression by all 13 of them. These ones stand out a bit more in their cruelty. Ishamael ultimately didn't want to be reborn anymore, Lanfear was obsessed with Lews Therin, Asmodean wanted to live forever and be a well known composer. Demandred, Be'lal, and Rhavin were jealous of Lews Therin's success. Mesaana wanted to be a researcher. They all did evil shit and didn't care about the people they hurt, but the ones in paragraphs above seemed to do it as the ends, rather than a means to an end.
Oh yeah, extra tidbit about Semirhage: she discovered that 13 channellers and 13 myddraal could be used to turn a channeller without torture required. But she preferred the torture way.
My guess is gonna be a Dr. Who or a Black Mirror villain that utilized deep psychological horror. Maybe one of the ones that made people into immortals or data-immortals with a near infinite amount of time combined with horrifying living conditions to break their victims.
The Mistress resurrected the dead all throughout earth and created paradise to turn them all into cybermen, android with a chip to prevent emotions, if that chip gets removed cybermen go into an agonizing pain due to realizing what they have become
Hades is far from being evil. He's a loyal husband and impartial/ fair when dealing with the dead. He even did a solid for Orpheus that one time and all. Too bad homie didn't follow Hades' clear instructions.
You could really take your pick of Vampire the Masquerade baddies.
Ur-Shulgi, for instance, who looks like a charred corpse, has led multiple genocides, is directly referred to as "violence incarnate," and doesn't seem to have a goal beyond exterminating everything he considers unclean. Depending on who you ask, that may very well be damn near everything, period.
Or Sascha Vykos, who... to call them a torturer is like saying Michelangelo kinda knew how to paint. Vykos is a monster in every sense of the word, and cruelty is both method and goal in a lot of their schemes.
The Endsinger is up there. FFXIV Endwalker spoilers follow.
spoiler
She was tasked with finding the meaning of life, but the vast indifference of the universe turned her into the incarnation of depression. She determined that life is pointless and invariably leads to suffering, and decided to end all life in the universe as a kindness. She made her nest at the edge of creation, where she gathered all of the souls of the dead to prevent their reincarnation and feed on their despair and suffering, to eventually grow powerful enough to accelerate entropy and bring about the heat death of the universe.
She was defeated by the power of friendship. And our best frenemy.
On second thought, Valens van Varro is worse. Fuck that guy.
The witch from the witches house game. I won't spoil it here but the second ending is really hearty breaking and cruel, I recommend you watch a playthrough of the game.
Let's see, the joker? No. Golb? No. Bill cypher? Good choice, but no. As stupid as this answer might be, for me, it's most likely homelander from the boys. Homeland is established to be a cruel, terrifying, and sociopathic villain who doesn't care about who lives or dies, and all though that can be said about the ither villans I had listed, homelander is diffrent. For an example, the joker kidnapped Jason Todd, tortures him, and became the ultimate reason red hood even kills, but homelander doesn't kill people to hurt someone else, he just kills because he likes it. The joker does everything he does to get closer to batman to mess with him, but homelander just wants to see blood. Another example, Bill Cypher torments Ford and uses the people of gravity falls as his puppets, but he does that because he felt restricted by his realms 2 dimensions and wanted to be a God. Homelander thinks he is God, and thus believes he can just do anything he wants, a decides not to commit mass genocide, but torment people one at a time and either convince them to kill themselves or kills them because he's done toying with them.