Gear 5 makes Luffy one of the strongest in the series but that was not the only reason he defeated Kaido.

SUMMARY

 Kaido lost his final battle against Luffy in One Piece , but that does not necessarily mean he was weaker than his opponent.
 Kaido got to the final fight with Luffy after taking on the Red Scabbards, five pirates of the Worst Generation, and his daughter Yamato, all powerful opponents who sapped his strength.
 Kaido was also using his powers to support Onigashima in the sky during the entire battle. In a fair fight, he could have possibly beaten even Gear 5 Luffy.

The fight between Kaido and Luffy was the highlight of One Piece‘s Wano Arc. The two clashed multiple times before their final fight in Onigashima, and each time Luffy faced a devastating loss. With new techniques, new tactics, and more at stake, Luffy and the samurai headed off to Kaido’s domicile and after a long and exhausting fight, Luffy came out on top. However, his victory is shadowed by the fact that, before taking on Luffy in his overpowered Gear 5 form, Kaido had fought many hard battles, and even then he only barely lost.

Quite possibly the best villain in One Piece, Kaido was a force of nature and was known as the King of Beasts and the World’s Strongest Creature. His durability and insane strength propelled him to the status of Emperor of Seas, so it was a genuine shock when a young upstart pirate such as Luffy beat him. Looking back at the battle, however, it was hardly a fair fight.

Kaido Faced Too Many Challenges At Once

Before the main fight between Luffy and Kaido, the villain first took on all of Oden’s powerful retainers. These samurai are very tough and some even journeyed with powerful pirate crews. Although Kaido defeated them, they dealt some damage to him, or at least made him exhaust some power. After that fight, Kaido took on Luffy, Kid, Law, Zoro, and Killer, five pirates of the Worst Generation, including three captains. Although he had Big Mom to help him, it was obvious that the main target was Kaido. Kaido sustained some damage, mostly from Zoro who slashed him in the same spot Oden did 20 years prior.

After facing all these members of the Worst Generation and the Akazaya Nine Samurai, Kaido’s daughter Yamato stepped into the ring. Yamato hated their father for chaining them in Onigashima and enslaving the people of Wano. Like their father, Yamato is extremely powerful and even once took on Ace, a commander of the Whitebeard Pirates. Yamato has not only eaten a Mythical Zoan Devil Fruit, they can also use the ultra-rare Conqueror’s Haki, the only power capable of actually hurting Kaido. Yamato stood up against Kaido until Luffy arrived, further weakening and exhausting him.

As if all these battles and ambushes weren’t enough, Kaido was also supporting the entire Onigashima with his cloud powers throughout the whole war. He could have simply dropped his clouds at any point in the fight and let everyone drop to their deaths, but he didn’t, probably because he wanted to preserve his arsenal and army. Still, holding up Onigashima further sapped Kaido’s strength. Finally, even after Luffy awakened his Devil Fruit and unlocked Gear 5, Kaido fought him on par and only lost in the final, massive clash.

Kaido Could Have Won A Fair Fight Against Gear 5 Luffy

Throughout the whole battle, Kaido was distracted, attacked, exhausted, and constantly straining his powers, so it was no surprise he lost. If it was a one-on-one fight, and he was in peak form, Luffy even in Gear 5 would have lost to Kaido. Considering how that battle went, Kaido should still be considered the pinnacle of strength in One Piece.