The most common idea in the One Piece community is that Kaido has a Mythical Zoan Dragon Devil Fruit. This idea is supported by multiple facts, like his inability to die and his reputation as “the strongest creature in the world”. Here are 5 Devil Fruits I think Kaido might have:
#Hito Hito no Mi Model: Oni
Kaido could have eaten a Mythical Zoan Oni Devil Fruit which has transformed him into a human. He isn’t originally a human. Rather, he is a Dragon, who has eaten the Hito Hito no Mi Model: Oni. This goes well in line with why he’s Immortal. Even if they put seastone cuffs on him, he will just revert to his original form and his skin cannot be penetrated, so that’s why he cannot die.
#Dragon-Dragon Fruit, Model: Orochi
In Kaido’s Jolly Roger there are 8 bones surrounding the skull, which is rather out of the ordinary. I was also questioning the meaning behind the symbols in the background, which is actually Kanji (八) and as I found out it has the meaning “eight“.
Straight out of japanese mythology, the 8-headed Snake Yamata no Orochi or the 8-headed and 8-tailed Japanese Dragon Orochi jumped right in my face and I believe that Kaido’s Jolly Roger strongly implies that this creature is the King of the Beasts’ power. So Kaido could have the Dragon-Dragon Fruit, Model: Orochi.
#Paper Paper no Mi
I think that Kaido may have the Paper Paper no mi, or something close to that. Yes I know that there has already been a Paper fruit in a game or a movie or something, but that’s not canon, so I’m not counting it. Kaido could have gotten his epithet because in battle, he creates/created many “origami animals” as weapons. People think that Kaido’s epithet comes from the fact that he has many fake zoans on his crew, but he only begun buying the SMILES from Doflmaingo a couple of years ago, and he has probably had his epithet for some time now, at least I would think so.
#Beast Beast Fruit, Model Typhon
Kaido could have the Beast Beast Fruit, Model Typhon. The Typhon is a Greek God who is the son of Gaia and Tartarus. That’s the reason why Kaido has 3 calamities, is “immortal” and has the temperament of a child.
#Kirin Kirin no Mi
Kirin often appears tigerlike in artwork so it is often confused with Byakko. However it truly is a unique diety as it is said to look like a deer with scales like a dragon’s covering its body and often has a great horn. It has a tail like an ox’s and a flowing mane. Its body and mane are covered in brilliant holy fire. Quite fitting for Yonkou who is called Hundred Beast Kaido, the Strongest Creature in the World.