Monkey. D Luffy is the protagonist of Eiichiro Oda's One Piece and he aims to become the King of the Pirates in a time known as the Great Pirate Era. In a plethora of pirates, Luffy aims to rise to the very top and become the freest man on the oceans. With his pirate crew, known as the Straw Hat Pirates, Luffy has, over the years, gained plenty of notoriety and made an incredible name for himself as well. His strength has gradually grown and, after the two-year timeskip, he's become tremendously powerful. In the Wano Country arc, he took the next big step on the big stage when he faced off against Yonko Kaido in a serious battle and gave him a run for his money. #
By the end of the fight, Luffy ended up gaining new powers that pushed him on level with Kaido and, eventually, even crush him in battle. With Kaido's defeat, he's now established himself as one of the very strongest characters in the world of One Piece and can now inevitably draw comparisons to the legends of the world, such as Whitebeard and Gol D. Roger, however, is he that powerful?
Luffy's Strongest Powers Right Now
Although Luffy was nowhere near the level of the legends of the One Piece world when the story began, he has grown at a staggering rate and has evolved into an extremely refined fighter. Having eaten the Gomu Gomu no Mi, Luffy has gained the power of rubber and while that in itself isn't all that amazing, the way he utilizes this power certainly makes it quite incredible. Luffy has the power of Gears, which he created during the Enies Lobby arc for the very first time.
With Gear Second, Luffy can dope himself by pumping blood faster through his body, and using Gear Third, he can inflate his bones to gain the limbs of a giant. During the two-year timeskip, Luffy created Gear Fourth, with which he inflated his muscles and gained stength great enough to send even the strongest of people, such as Kaido, flying with his elastic powers.
At the same time, Luffy learned all three forms of Haki during the two-year timeskip under the guidance of Rayleigh. Although Luffy only managed to learn the basics during this time, he then went on to advance it through the many battles that he fought and got even stronger. Luffy gained the power to use advanced Observation Haki during the Whole Cake Island arc when he faced off against Katakuri.
With this power, he gained the skill to see the future. During the Wano Country arc, Luffy trained in Udon Prison and managed to advance his Armament Haki to the next level. In doing so, he gained the ability to destroy his targets from within by sending his Haki directly into their bodies. During the fight against Kaido, Luffy then went on to gain the advanced form of Conqueror's Haki and coat his body in it. By doing so, he could inflict serious injuries on someone as tough as Kaido and even fight him on an equal footing.
While all this already makes him strong enough to compete with a Yonko, at the very least, Luffy took things a step further by awakening his Mythical Zoan Devil Fruit. Thanks to his awakening, his rubber body got even tougher and he gained even more freedom in combat. At the same time, Luffy reached his peak as a fighter and gained a new form called Gear Fifth. In this state, Luffy became powerful enough to overwhelm the likes of Kaido in combat and became a true equal of his.
Is Luffy As Strong As Roger And Whitebeard?
In all of One Piece, the Pirate King, Gol D. Roger, and his rival Whitebeard are considered to be the strongest known pirates to ever live, with Rocks possibly making a case for himself as well. Roger conquered the entire world with his mighty Haki and became the King of the Pirates while Whitebeard ended up matching him in combat by using the power of the Gura Gura no Mi and even mastering all forms of advanced Haki. The two were considered to be monsters in their own league during their primes, and for Luffy to match them in combat would certainly take something special.
Yet with everything that Luffy has gained over the years, he's fit enough to be compared to the legends of the One Piece world. Kaido, who Luffy just defeated, was powerful enough to draw comparisons to Whitebeard and Roger. In fact, Kaido was widely known to be the strongest pirate alive and, what's more, the strongest creature out of all living things. His performance throughout Onigashima certainly put him on the same level as the likes of Whitebeard and Roger or, at the very least, close to them.
For Luffy to defeat Kaido means that Luffy, too, has taken a big step towards becoming a pirate of the same caliber as Whitebeard and Roger. While it is true that the likes of the Red Scabbards, Yamato, and even some members of the Worst Generation aided Luffy in the fight at different times, the fact remains that Luffy took an attack powerful enough to actually kill him due to an unfair interference from a CP0 agent.
If anything, Luffy took more damage than Kaido did and yet he managed to defeat him in a true one-on-one battle, something that nobody has ever done in history – not even the likes of Whitebeard or Roger. While it is true that Luffy can still get stronger as a pirate and he most certainly will advance his Haki further, it goes without saying that even now, he's worthy of being compared to the mightiest pirates who ever lived.
Luffy's strongest technique, called Bajrang Gun, saw him create an island-sized fist and coat it with Armament and Conqueror's Haki. This technique could easily level an island and cause tsunamis and is what ended up defeating Kaido.
Until now, no character, not even Whitebeard with his Gura Gura no Mi or Roger with his Haki, has shown an attack that powerful. Luffy not only has incredible Haki but also has a Devil Fruit that bears the name of a God. As such, he is undeniably in the same league as the legends despite not being a true equal to them in terms of strength just yet. With a bit more time, however, Luffy will certainly surpass them.