Voldemort may be super creepy, but you'll be surprised who beat him on this list ...

Trolls may be the stupidest monsters in the Harry Potter universe, but they can certainly be a nuisance when they're let loose in a school bathroom.

Monsters don't have to be supernatural. Harry's aunt, uncle and cousin are a group of bitter Muggles (non-magic folk) who treat the young wizard horribly.

You don't want to single out all of Slytherin, but Hogwarts definitely has its slew of bad apples. When you have to use magic to ward off a bully, things have crossed a line.

A mature mandrake's scream, after it's unearthed, can kill any person who hears it. Their biggest crime? These plants are really annoying.

Honestly, this tree is just straight-up petty.

Though these winged horses are "quite gentle," according to Luna Lovegood, they have a bad reputation. They can only be seen by people who have witnessed death.

Something about Barty's darting tongue and manipulative ways makes him one of the creepier Death Eaters.

Hagrid's three-headed pet dog, Fluffy, is vicious. You do not want to cross this pooch without a soothing soundtrack to lull him to sleep.

Umbridge may not be a monster, per se, but as a person who regularly abuses her position of power, she is certainly someone you do not want to encounter.

We'll never look at Disney's The Little Mermaid the same way again.

Though some dragon keepers try to train them, these fire-breathing beasts are among the most dangerous beings in the wizarding world.

Another one of Hagrid's unsettling buddies, this giant spider has a taste for human flesh. Gross.

The most fanatic Death Eater of the bunch, Voldemort's most loyal follower commits terrible acts, including murdering house-elf Dobby and torturing Neville Longbottom's parents.

Though some werewolves can be super nice (shout out to Remus Lupin), there are others who are truly frightening. Fenrir Greyback is a terrifying beast who has a habit of attacking children.

Snakes. Why did J.K. Rowling have to include snakes? The King of Serpents, bred by Dark Wizards, kills anyone who makes direct eye contact with it. RIP Moaning Myrtle.

He-Who-Must-Not-Be-Named is the most powerful, and most chilling, Dark Wizard of all time. He will destroy anyone in his path, plus he looks like a human snake ... and that's creepy.

Dementors are faceless, dark beings that will suck the soul out of you. These personified nightmares are by far the creepiest things in the Harry Potter universe.