Befitting his bulk, Kaido is legendary for his supreme physical power as the strongest creature in the world. He possesses nigh-indestructible durability, even without using Busoshoku Haki!
He took multiple powerful hits from Luffy’s Gear Third while in his dragon form and transformed back into his human form after being pummeled into the ground, and proceeded to receive a barrage of Gear Fourth hits that were even more powerful, yet he felt nothing more than annoyance, received no injuries, and was able to quickly get back up and counterattack without issue.
Kaido also clashed with Big Mom continuously for one to three days, and emerged without any injuries.
While the Red Scabbards were able to accomplish the rare feat of drawing blood from him with their swords and attacks, these wounds were shown to have very little effect on him, with Kaido himself stating that the injures were shallow.
This durability has given Kaido the reputation of being unable to die.
The only known time Kaido ever suffered a significant injury was in a battle against Kozuki Oden, a legendary samurai who was dual-wielding two of the twenty-one Great Grade swords, Enma and Ame no Habakiri, gaining the only scar on his body.
We already knew that in his dragon form, Kaido can release devastating blasts of fire from his mouth, which can instantly deal significant damage to, if not completely obliterate, a large area or structure.
But as we have seen in chapter 933, aside from fire, Kaido appears to be capable of releasing other elements such as blasts of lightning and wind that turns into air blade projectiles from his mouth, which was able to slice off Kikunojo’s arm.
Since Kaido has a Mythical Zoan-type Devil Fruit, aside from high speed regeneration, we can expect even more!