Minotaurus

Minotaurus is one of the four Demon Guards in Impel Down. He is an actual minotaur (not a Zoan Devil Fruit user, as first speculated) and the first of the four to be introduced.

Appearance
Minotaurus is a dumb looking minotaur with cutesy eyes, large lips, and a runny nose. His body pattern resembles that of a Holstein cow. He wears pants but no shirt. He is often seen with a spiked club that he uses. Before his appearance was fully revealed, he was seen in silhouette and appeared extremely savage and truly demonic due to his actions. Like the other guards, Minotaurus has a comical and harmless appearance, despite their true power and personality.

Personality
A cold, heartless Demon Guard! A monster who treats humans like so much trash! — Mr. 2 Bon Kurei describing Minotauros

Despite his ridiculous appearance, Minotaurus is a cold blooded beast. He would brutally bludgeon rioting prisoners and opponents alike with his spiked club. He would often do so aimed at their skulls. Because of his savagery, the various prisoners of Impel Down fear him, like the Demon Guards.

Abilities and Powers
While he doesn't look like a powerful opponent, Minotaurus is in reality a fearsome beast. He has immense physical strength and speed, along with excellent resilience. Wielding his spiked club as a weapon in conjunction with these attributes, he is a lethal force to be dealt with.

History
It is first seen beating two prisoners up for fighting and locking them up in a cell for death row, then again beating Jinbei in Level 6. Although only its shadow is shown during those times, it is clear that it is a Minotaur that shows no fear. The fact that it could beat a strong character like Jinbei until he is covered in blood suggests how strong it is (though at the time, Jinbei was chained down).

Later as Luffy reaches the Starvation Hell of Impel Down, it gets the order to battle him as well as Mr. 2 Bon Kurei, who was supporting Luffy. However, as soon as it sent Mr. 2 flying with a single hit, Luffy recognized its true powers and immediately activated Gear Second and used his Jet Bazooka to send Minotaurus flying to save Mr. 2.

Although Luffy used one of his powerful techniques to defeat Minotaurus, it appeared later, hunting Buggy and Mr. 3 (it landed on top of them when Luffy sent it flying). At one point they come to meet Luffy and Mr. 2. Buggy used his secret weapon, the Muggy Ball, to take Minotaurus down, but even after a huge explosion it was still conscious. Even when Mr. 2 used a strong kick to finish it off, it stood still but was in great pain. Only as Luffy and Mr. 3 combined their abilities to use the Gomu Gomu no Tonkachi Rifle, they could fully defeat Minotaurus. Was last seen falling from level 3.

Trivia

 * Zoro's design for Mugiwara Theatre - Monster Time is similar to Minotaurus in many ways. Both carry identical clubs, are minotaurs that resemble cows and both have patches in similar places to each other.
 * Minotaurus' name is a combination of Minotaur and Taurus, the latin name for bull. This naming combination is shared with his fellow Demon Guards.

Links

 * Minotaur - Wikipedia article on the mythical monster.
 * Holstein - Wikipedia article on the bovine breed of Minotaurus.