The Straw Hats of the One Piece universe have come across many unique faces on their adventures. Some are silly - cantankerous clowns, conniving game hosts, and even singing trees.

RELATED: 10 Anime Villains Who Just Let The Hero Win

However, there are an equal number of horrific monsters that the heroes encounter. Whether through appearance, behavior, or a combination of the two, their character designs are so harrowing that they'd send a chill down the spine of any ordinary person.

10 Kuma Is A Massive Man Who Lost His Humanity

Kuma Looms Over The Straw Hats In One Piece

Kuma was one of the Seven Warlords and among the most difficult opponents who the Straw Hats faced before the time skip. Although he looks mostly human, it belies the mechanical way he walks and speaks.

There are a number of other terrifying qualities that accentuate Kuma's threat. Not only does he tower over every Straw Hat by over three times their height, but there are also multiple versions of him called "Pacifistas." Even his duplicates strike dread into the most intrepid pirates, as seen during the battle for Marineford.

9 Magellan Was Especially Scary In His Venomous Form

Magellan Poison Fruit

As the prison warden of Impel Down, Magellan's venomous form conveys him as a vicious, viscous nightmare. Anyone foolish enough to touch him would be afflicted with fast-acting poison, making him a viable threat even against armament Haki users.

Perhaps more dauntingly still, he has a final form that turns his body into a reddish pink. When using it, his body becomes highly acidic, even burning through solid steel in a matter of seconds. The only thing that detracts from Magellan's scariness is the fact that he's constantly on the toilet.

8 Despite His Friendliness, Brook Is Still A Skeleton

Brook from one piece

When the crew first met Brook, they were understandably distrusting of him. He serenaded them with haunting music from atop what they presumed to have been a lost ship. After meeting him, they learned that he was a good person who simply ran afoul of bad luck.

Despite Brook's friendliness, he's still intimidating as a talking skeleton. This was especially true with his pre-time skip character design, where he wore drab, Victorian clothing as opposed to his recent outfits, which reflect the gaudiness and commercialism of a successful modern musician.

7 Big Mom's Size & Mannerisms Make Her Terrifying

big mom from one piece

Big Mom is one of the few characters in fiction who is capable of making a pink dress look intimidating. In addition to being a giant of a woman (towering over buildings and capable of destroying them with ease), she also has a wicked grin and sunken eyes.

RELATED: One Piece: 5 Ways Hody Jones Was Right (& 5 He Wasn't)

Perhaps the most daunting aspect of her character is that, as hard as she tries to appear friendly, neither audiences nor the series' cast is able to see her as anything other than a serious threat. Considering how willing she was to destroy her own people over a dessert, any reservations are understandable.

6 Ryuma Was The Series' First Intimidating Zombie

ryuma from one piece

One Piece tends to treat zombies as novelties. When the crew first arrived on Thriller Bark, Luffy was as bold as to put one of the undead back in the ground seconds after they sprung up.

However, Ryuma proved that not all of his kind were so easily subdued. He defeated Brook both times they fought and would have even killed him if he didn't need his shadow. Ryuma is particularly intimidating given his exposed teeth, eyeless leer, and desiccated skin.

5 Zunisha Was A Beast Tall Enough To Sustain Civilizations

zunisha versus jack in one piece

Zunisha was arguably the series' largest animal. He could have been mistaken for a wandering island and sustained the entire Mink civilization on his back. More jarringly still, he had sunken eyes, shriveled skin, and a listless stare, much like those of a zombie. Many of the people he supported had no idea he was even sentient.

RELATED: One Piece: Doflamingo's 5 Greatest Strengths (& His 5 Worst Weaknesses)

Although usually passive, the elephant displayed his incredible power when thwarting Jack's forces. He obliterated the pirate's entire naval armada with a single sweep of his trunk.

4 Hody Jones' Enhanced Form Was The Stuff Of Nightmares

Hody Jones glaring evilly in One Piece.

Between his scratchy voice and virulent racism, Hody was already scary enough in his standard form. After consuming an inadvisable amount of energy steroids, he turned into an entirely greater menace.

His muscles swelled beyond reasonable proportions (even by One Piece standards), and his teeth grew past his jaws' ability to support them. Hody's most intimidating feature was how his massive face frames his beady blood-red eyes. In the end, he served as a compelling metaphor for the dangers of what happens when hatred dominates a person's entire life.

3 Kaido Was A Mountainous Man Feared By The Entire World

kaido from one peice

As an emperor of the sea, Kaido already had a reputation as a nearly unstoppable killing machine. This was substantiated through his conquest of Wano, one that prompted Kin'emon's journey across the New World.

Kaido showcased his monstrous invincibility during his first appearance, where he survived falling from the sky with negligible injury. His legend was so profound that he was mentioned as early as Thriller Bark, when Gecko Moria blamed him for ruining his life.

2 Oars Was An Undead Giant That Could Mimic Luffy's Power

Oars the Continent-Puller

Oars was a giant that Gecko Moria revived in order to reclaim his position of prominence on the global stage. Although his colossal stature already rendered him a serious threat, Luffy's shadow allowed him to imitate the effects of the Gum-Gum fruit. Additionally, the villain's immunity to pain allowed him to fight without tiring until his body fell apart.

As a result, the Straw Hats failed to defeat him even with their combined efforts. Only a shadow-enhanced Luffy was able to put an end to the creature, save his crew, and finish off Gecko Moria before the sunrise incinerated everyone.

1 Smiley Was A Noxious Blob Full Of Poison Gas That Consumed Anything It Touched

smiley one piece

Smiley was a gigantic slime creature created by Caesar Clown. It was large enough to spread its entire body across Punk Hazard, and slicing it apart only divided it into smaller sentient blobs. As a result, the Straw Hats couldn't actually defeat it. They could only run away.

Caesar put an end to Smiley by feeding him a candy that turned his body into gas. He had hoped to use it to prove the potency of his bioweapon to potential investors across the world.

NEXT: One Piece: 10 Ways Caesar Clown Could Have Won At Punk Hazard