As one of the Yonko, Kaido is among the 4 strongest pirates alive. He’s renowned as the “Strongest Creature in the World”.
Notably, Kaido has a bounty of 4,611,100,000 Berries, which is the highest of any pirate currently alive, surpassed only by the bounties of the late Whitebeard and Gol D. Roger.
Kaido attempted to take Whitebeard’s life, something few would dare, and subsequently clashed with Shanks. When Gekko Moriah was in his prime, Kaido fought him and emerged victorious, having killed his entire crew.
Kaido defeated another member of the Worst Generation, Eustass Kid, whose bounty is 470,000,000 Berries, with apparent ease.
Kaido has a very strong will, as shown when he was completely unaffected by Luffy’s Haoshoku Haki. He also possesses nigh indestructible durability, even without using Busoshoku Haki.
This durability has given Kaido the reputation of being unable to die. He has been caught and tortured 18 times, and people as powerful as the Marines and other Yonko have attempted to execute him 40 times only to fail as Kaido survived every single attempt because every single execution weapon broke when being used on him. Most notably, Kaido has jumped from 10,000 meters from the sky onto the ground, creating a massive shockwave strong enough to sink a large ship nearby, and emerged only with a headache; it has even become a hobby for him to attempt suicide, only for it to fail.
Kaido has eaten a Mythical Zoan-type Devil Fruit that allows him to transform into a massive, blue-scaled Eastern dragon, notably with a circle of flame around each of his upper arms. In this form, he is capable of moving through the air by creating clouds and using them as footholds. He can also release devastating blasts of fire from his mouth, which can easily blow apart a large area.
Kaido is extremely fast despite his massive size, as shown when he moves past Luffy in an instant while attacking him.
Kaido defeated the “Fifth Emperor” with just a single blow.. how could Luffy defeat him?
In one of the interviews, Oda said that he doesn’t know how Luffy should win because Kaido is incredibily powerful: “When Kaido appeared for the first time, I said that Luffy can’t defeat such a strong character yet. And I’m yet to know how Luffy would defeat Kaido. Probably my audience will not be satisfied if the reason for defeating Kaido is just because Luffy’s punch is so strong. Luffy and I have to find a solution somehow.”