Despite the wholesome face that Pokemon puts out into the world, there are plenty of lore elements out there that may change the games' kid-friendly rating if they were more commonly known. There are some truly fearsome Pokemon out there. They can control the forces of life and death or hold the power to burn the world.
With some Pokemon, this may not be that surprising. However, some of the most horrifying Pokemon are the sweet little cuties that people cherish. Evolution in this world clearly knew that people gravitate to cuteness and found it the easiest way to lure in more prey.
10 Misdreavus - Feeding On Fear
Ghost Pokemon are a main-stay of the "evil" category. No other Pokemon type has such a clear-cut connection with the supernatural and what lurks on "the other side" of death. Misdreavus is a small and cute Pokemon that would lure anyone in. It even has some nice jewelry.
That said, its name is a pun on mischievous, so it's clear there's more than meets the eye. As expected, it's quite the prankster. It often screams in the middle of the night to startle people, as well as make ghostly crying noises to frighten them. This could be a bit endearing if that was all it was, but the reason it does this is that it feeds on the fear these actions cause, which gets absorbed into the red orbs around its neck.
9 Pumpkaboo - Hypnotic Flames
Many terrifying Ghost Pokemon have quite cute pre-evolutions, and Gourgeist is no exception. Some may even say Gourgeist is cute itself, but not quite as much as Pumpkaboo. This Jack O' Lantern with a face is oozing with charm.
Pumpkaboo has an interesting quirk, which is that it can actually vary in size when encountered. Its size is determined by where it grows. The more lost souls that wander the area, the larger it gets. It's not intentionally evil, as when these lost souls are absorbed, they are moved on to the afterlife, where they belong. However, a Pokemon that absorbs the souls of the dead and grows larger as it does so is a terrifying thought.
8 Sandygast - Even Sand Is Out To Get You
Sandcastles are fun! It's something everyone's done at least once when they've visited the beach, and with the shores of Alola being lined with so many beaches, there's bound to be tons of leftover sandcastles waiting for the tide to take them.
The Pokedex warns against leaving them, however, because this is the world of Pokemon where anything can become possessed if people stop looking at it for five seconds. This cute little mound of sand "embodies the grudges of the departed" and will take control of anyone who touches it and force them to pile more sand onto their bodies to get bigger.
7 Nickit - A Remorseless Scavenger
Like most urban foxes, Nickit scavenges for its food. It's an exceptionally cute Pokemon with a cool expression and timid smile that seems designed to make people feel sorry for it and hand over some grub.
It's all a facade, though, as this Pokemon lives on ill-gotten gains and steals food from wherever it can find. It's got a sharp snout to reach into hidey-holes and drag things out, big ears to hear threats coming, and its tail wipes along the ground and clears its tracks as it walks. It cares not for the Pokemon it steals from, who may very well starve, and just looks out for number one.
6 Mimikyu - Copycat Killer
Despite doing creepy things for creepy reasons, a large portion of Pokemon fans has fallen in love with Mimikyu. The way it wants to look like Pikachu combined with the tattered cloth it wears that looks like a child drew it has drawn people to love this absolutely horrifying monster.
For one thing, there are several notes in the Pokedex of anyone who has ever looked at Mimikyu's true form simply dropping dead later that day. Then there's the fact that its unique Z-Move is called "Let's Snuggle Forever". If that doesn't say, "I'm trying to kill you," then nothing will. The fact that the creature under the cloth is too shy to be out in the open might be the only thing that's stopping it from wiping out life on Earth.
5 Ninetales - A Curse Upon You
Ninetales is an unexpected Pokemon to be so brutal. It's not a Ghost-type, and there's nothing inherently creepy about its design. It's pre-evolution, Vulpix is a nice, cute fire-fox. However, those people have clearly never got on a Ninetales' bad side.
The Pokedex describes it as "Vindictive and relentless". It's highly intelligent and can manipulate its flames to hypnotize people. The kicker, however, is that it has the power to inflict generation-spanning curses on those who cross it. Curses which, according to the Pokedex, can last up to 1000 years.
4 Ditto - Bodysnatching
Ditto's an interesting case because the games and anime generally present Ditto as a more comedic figure. They copy people to play pranks to or defend themselves, and they have hilarious simplistic faces. It's very endearing, but fans are all too aware of the implications this ability can have.
Ditto's copying ability has basically no limit. While it does have to rely on its own memory from time to time, as far as the Pokedex is confirmed, it can create a copy of someone on a cellular level if they're looking at what they want to copy. Plenty of Creepypasta-style stories are out there of Dittos replacing people without anyone knowing until it's too late, turning it into a very creepy Pokemon.
3 Phantump - A Child Forever Lost
This little tree stump is one of the cutest Ghost types out there, it seems like it'd be very playful, and it is, but not for nice reasons. Phantump is an unfortunate Pokemon, as it causes its own reproduction by complete accident.
Phantump is a tree stump that has been possessed by the spirit of a lost child who couldn't find their way out of the woods. This is creepy enough, but Phantumps imitate children's laughter in order to lure people into the forest. They're trying to make friends, but all they do is cause more children to become lost, and thus, more Phantump are created.
2 Litwick - Burning The Soul
While plenty of cute Ghost Pokemon do horrible things, it's not often with outright malicious intent. The fully-grown Ghost Pokemon know exactly what they're doing, but with the babies, there's often an implication that they just don't know any better. Litwick is the exception to this rule.
Litwick pretends to be a guide for lost people and Pokemon. It takes them by the hand and, to quote the Pokedex, "Guides them to the afterlife". It then feeds on their life energy and leaves them as a husk, burning that energy as the flame on their head. There's no naivety here, Litwick knows what it's doing, and it does it with glee.
1 Drifloon - Just Straight-Up Killing Children
For the first few generations, after it was introduced, Drifloon seemed a bit hapless. It floated about fairly aimlessly and didn't seem to have the strength to pull back on people who grabbed it. However, even back then, it was still trying to "Steal children away", even if it didn't do a very good job.
In later generations, though, its Pokedex entries got less generous, and Drifloons nature as a cold-hearted killer of children was made apparent. According to the Sun & Moon Pokedex, it grabs their hands and "drags them away to the afterlife", after it does this, it absorbs the soul inside of itself and the balloon. Popping the balloon sees the souls it has inside spill out with debilitating screams. Drifloon is one Pokemon that trainers should run far away from as soon as they see it.