One Piece - Kaido of the Beasts

Kaido of the Beasts is one of the Yonko, and the third one to be mentioned by name. He is also one of the central antagonists of the Pirate Alliance Saga. According to Trafalgar D. Water Law, Kaido is known as the strongest creature in the world. Kaido's name was first mentioned by Gekko Moriah shortly after having obtained Luffy's shadow. His title of Yonko was revealed just after the Straw Hat Pirates defeated Moriah. Though not much is known about Kaido's physical appearance, he was originally portrayed as having a wide face, pointy nose, sinister grin and one visible eye on the right side of his face upon being revealed in silhouette during the Post-Enies Lobby Arc.

However, like Charlotte Linlin, this could have been an early design by Oda, and have changed. From what is shown, Kaido is a merciless and confident warrior who never lets an opportunity slip by, as evidenced by his plan to attack Whitebeard during the latter's attempt to save Portgas D. Ace from execution. He is also pitiless and not open to negotiations and excuses, which makes it seemingly unwise to provoke or underestimate him. This is enforced dramatically when Donquixote Doflamingo, a Shichibukai and World Noble known for his fearless and confident attitude, is very afraid of Kaido when he may be unable to fulfill his end of their accord due to Trafalgar D. Water Law holding Caesar Clown as a hostage. It was also stated by Scotch that Kaido has a favorite island, a winter island that was guarded by the cyborg and visited by X Drake. He has some care for his subordinates, or at least values Scotch, as Scotch confirmed that Kaido would be angry if Scotch were to be attacked.

As one of the Yonko, Kaido is one of the strongest pirates in the world. He attempted to take Whitebeard's life, which is something that few would dare, and clashed with Shanks. He also once fought against Gekko Moriah of the Shichibukai, and emerged victorious. Being a Yonko in and of itself is a testament to his power. It was also stated by the Gorosei that he is one of the few people capable of stopping Blackbeard. According to Law, he is said to be "the strongest creature in the world" (この世における最強生物 kono yo ni okeru saikyō seibutsu?), insinuating that he is not even human, and suggested that he can easily kill Doflamingo, who is a world famous pirate and a Shichibukai. Further testament to his strength is that Law speculated that even with an alliance with the Straw Hats, their chance of defeating him is only about 30%. Similar to the other Yonko, Kaido also seems to have many underlings and allied pirates, and is able to claim islands as his own territories. With Caesar and Doflamingo as his associates, Kaido has created an army of over 500 Artificial Zoan-class Devil Fruit users.