Kaido, one of the Four Emperors of the New World in the One Piece series, is known for his incredible strength and formidable power. He has been a major antagonist in the series and has had several confrontations with Monkey D. Luffy, the main protagonist of the story.
To answer the question, Kaido has defeated Luffy only once so far in the series. This happened during the Wano Country Arc, which is the current arc in the One Piece manga and anime.
The confrontation between Kaido and Luffy took place on the rooftop of the Onigashima Dome, where Kaido had been waiting for Luffy to arrive. Luffy had been training and preparing for this battle for a long time, and he had gathered a powerful alliance of samurai, pirates, and other allies to take down Kaido and his crew, the Beasts Pirates.
In their initial clash, Luffy managed to land some blows on Kaido and even activated his new form, Gear Fourth: Snakeman. However, Kaido’s incredible durability and strength allowed him to withstand Luffy’s attacks and counter with his own devastating blows. In the end, Kaido defeated Luffy with a single punch, knocking him out and leaving him badly injured.
Despite this defeat, Luffy and his allies did not give up and continued to fight against Kaido and his crew. They regrouped and launched a second attack on Onigashima, which is currently ongoing in the manga. Luffy has vowed to defeat Kaido and bring him to justice for all the harm he has caused to the people of Wano Country.
It is worth noting that Kaido has faced several other powerful opponents in the series and has emerged victorious in most of these battles. He has also been shown to have an incredibly high level of endurance and resilience, making him one of the toughest opponents that Luffy has ever faced.
In conclusion, Kaido has defeated Luffy only once in the series, during their initial clash on the rooftop of the Onigashima Dome. However, Luffy and his allies are currently engaged in a fierce battle against Kaido and his crew, and the outcome of this fight remains to be seen.