One Piece's Wano Country arc is currently at its very peak as the fight between Luffy and Kaido seems to have finally settled down. Having taken the first big step towards becoming the greatest pirate on the seas by matching Kaido in battle, Luffy aimed to defeat him in combat and free Wano Country in doing so. The task at hand wasn't nearly as easy, however, as Kaido is, without a doubt, the strongest opponent that he had faced to date. Luffy's clash against the Yonko saw him lose thrice before he was able to fight Kaido on the same level.
The first clash between the two ended in a crushing defeat in Kuri, while the second saw him fall off Onigashima having been knocked out. Luffy also died once in the fight against Kaido, however, that ended up making him even stronger as he awakened his Devil Fruit and tapped into the power of Gear 5th, unlocking a host of new abilities and easily what is the strongest technique of Luffy so far in the story.
What Is Luffy's Bajrang Gun?
Thanks to the power of Gear 5th, Luffy's body gained even more freedom and his rubber abilities strengthened even further. Along with gaining a new transformation, Luffy could also affect his surroundings and turn them into rubber. The power-up is an immense one and allows him to size up his body as much as he likes and then manipulate it to different forms immediately after without the need to use Haki to manipulate it.
While Luffy pulled off quite a few ridiculous tricks in the fight against Kaido, such as turning the Yonko into rubber and even grabbing a lighting bolt and hurling it towards him, his biggest feat in the fight remains to be what appears to be his ultimate attack, called Gomu Gomu no Bajrang Gun. The attack sees Luffy use the very pinnacle of his Devil Fruit powers and create a massive fist. Unlike Gear Fourth, Luffy doesn't need to blow air into his arms anymore. Instead, Luffy can simply create a massive fist using the newly awakened powers of Gear 5th and launch it towards his enemies.
The size of the fist that he creates is greater than any that his previous Gear Third or Gear Fourth attacks. In fact, the size of the Bajrang Gun is so massive that it could well be comparable to Onigashima itself. A fist as big as an island is surely great enough to do colossal damage and easily ranks among the strongest techniques seen in the entire story to date. To match Luffy's Bajrang Gun, Kaido had to pull out his strongest form, called Blazing Fire Dragon, which gives him the power to manipulate excessively hot flames that can vaporize anything they touch within an instant.
How Strong Is Luffy's Bajrang Gun?
Luffy's Bajrang Gun is, without a doubt, one of the strongest techniques seen in the entirety of One Piece. According to Luffy, this attack is powerful enough to send the strongest Yonko crashing down to the bottom of hell in a single blow, meaning it holds enough power to completely knock a Yonko out, which is utterly ridiculous. To use this technique, Luffy grabbed Kaido with one of his hands and used his other to create an island-sized fist.
While this on its own is capable of doing large-scale damage, Luffy then coats his fist in Armament Haki and Conqueror's Haki, and, what's more, both of these Haki types are being used in their advanced forms. He then wwnt on to retract his fist inwards, just as he does with his Gear Fourth attacks to increase their power even further. A hit from a fist this massive would easily be great enough to wipe out an entire island off the face of the earth and even cause tsunamis.
To put things into perspective, very few island splitters have been seen in One Piece so far. Blackbeard's Gura Gura no Mi is known to hold the power to destroy the entire world with its quakes, Shirahoshi's Poseidon powers are known to be great enough to summon Sea Kings and sink any island with ease. Finally, the warship, Pluton is known to hold the power to destroy entire islands in a single shot. Especially, Luffy can do something similar to an Ancient Weapon with a single punch of his.
Gomu Gomu no Bajrang Gun is strong enough to not only destroy an island but also cause large-scale destruction around the island, possibly leading to giant tidal waves and even tsunamis. Luffy eventually managed to land this hit on Kaido as the fight neared its conclusion. Once it landed and sent Kaido crashing down, fans got to see how much Luffy has grown as a pirate and how immense his strength is. Luffy is, without a doubt, ready for the big stage and is already among the most powerful pirates in the world of One Piece. With the defeat of Kaido, this fact has been further solidified and given Luffy a great status in the One Piece world.