In the world of One Piece, the four most powerful pirates are known as the Yonko, the Four Emperors, four fearsome captains who rule over the New World, the most dangerous part of the Grand Line. Constantly at war with each other, they command enough military power to topple a nation with ease, which puts the Yonko at the top of the list of the most wanted criminals by the World Government and the Marine.
When they were introduced, the Yonko were legendary figures shrouded in mystery. As the series progressed and Luffy and his Straw Hat Pirates got stronger and more involved with the big affairs of the world, the Yonko made their appearance and proved to be worthy of their title. All the Emperors can be counted among the strongest individuals in the world just in terms of personal power, without considering the vast resources at their disposal.
The legendary pirate Whitebeard was one of the Yonko, controlling earthquakes with the powers of his Gura Gura no Mi Devil Fruit and commandeering a vast fleet of faithful followers who considered him their father. After his death during the Summit War, Whitebeard's spot was taken by the treacherous Blackbeard. Let's have a look at who the Yonko are and why they are considered the apex of the pirate world.
Kaido of the Beasts
After Whitebeard's demise, the most powerful of the Yonko is likely Kaido, known as "the world's strongest creature," and the living pirate with the highest bounty in the world, 4,611,100,000 Belly. Kaido was born in the Kingdom of Vodka, where war was used to collect spoils to pay the tribute to the Celestial Dragons, the tyrannical rulers of the world. Kaido showed incredible strength as a child soldier, and for this reason his king sold him to the Marines in exchange for a seat at the Reverie. Kaido escaped and became a pirate, joining the infamous Rocks Pirates, a dangerous crew that produced many future Yonko. Years later, Kaido invaded Wano Island, enslaved its inhabitants, and turned it into a weapons factory, all for his goal to raise an army powerful enough to destroy the balance of the world, where a person's status is based on birth and wealth rather than strength.
As the captain of the Beasts Pirates, Kaido commands a mighty force of 20,000 soldiers, including an unusually high number of Zoan-type Devil Fruit users. What makes Kaido worthy of the Yonko title, however, is his personal power. Kaido possesses strength and resilience that is second to none. He is one of the very few individuals in the world capable of using all three types of Haki, including the extremely rare Haoshoku Haki. If that weren't enough, Kaido's Devil Fruit allows him to transform into a colossal Azure Dragon, capable of breathing fire and generating hurricanes, besides greatly boosting his physical abilities in his Hybrid Form. Kaido has no weaknesses, and Luffy was able to take him down only after a long and gruesome war, thanks to the help of many allies.
Big Mom
One of the most unique characters created by Eiichiro Oda, Big Mom (Charlotte Linlin) is a colossal old woman who dreams of creating a "perfect country" where members of all races will be able to live peacefully. However, this dream hides Big Mom's nature as a ruthless tyrant, as anyone who goes against her will is mercilessly punished. Big Mom's past is a bit of a mystery. Linlin's monstrous strength and temper tantrums as a child made her parents abandon her on Elbaf, the land of the giants, where she was raised by Mother Carmel, a child trafficker who wanted to sell her to the World Government and then mysteriously disappeared, leaving Big Mom with the powers of her Devil Fruit (there is a possibility that Linlin ate Carmel in one of her recurring fits of hunger).
Big Mom is also the matriarch of the very large Charlotte Family, whose many children make up the infrastructure of her crew. Over the years, Linlin became one of the most powerful pirates in the world, gaining a bounty of 4,388,000,000 Belly, the highest after Kaido's. Big Mom's monstrous strength and resilience are complemented by her mastery of all three forms of Haki, and by the powers of her Soru Soru no Mi Devil Fruit, which allows her to extract souls from people and infuse them into objects, creating beings called Homies that act as her servants. Big Mom was finally defeated by the combined forces of Trafalgar Law and Eustass Kidd, but only after the two captains awakened their Devil Fruit powers.
Red-Haired Shanks
Shanks is at the same time a very familiar character and the most mysterious of the Yonko. Appearing in the very first chapter of One Piece, Shanks is a veteran pirate who gave Luffy his iconic straw hat and inspired him to start his own journey. Years later, readers found out that Shanks had become one of the Yonko, and he was feared and respected even by powerful individuals such as Kaido and Whitebeard. As a kid, Shanks was actually a rookie on the ship of the legendary Gol D. Roger, the Pirate King, so it is only natural that he became a great pirate himself.
Besides his time on Roger's ship, nothing is known yet of Shank's past, his motivations, or even his true strength. One interesting theory posits that Shanks is actually the son of a Celestial Dragon, which would explain why he seems to have access to the World Government's most sacred place, Marijoa, and the Five Elders do not treat him like one of the most wanted men in the world, despite his bounty being an impressive 4,048,900,000 Belly. Shanks is also capable of using Haoshoku Haki, and he is one of the very few people in the world who were able to wound Kaido in a fight.
Blackbeard
The latest addition to the Yonko is Marshall D. Teach, Blackbeard, a treacherous villain even by pirates' standards. Blackbeard was once in Whitebeard's crew, serving under fleet commander Ace, Luffy's brother, but he killed one of his companions to steal the Yami Yami no Mi, one of the most powerful Devil Fruits, which gave him the power to control gravity and to negate other Devil Fruit abilities. At the height of the Summit War, Blackbeard appeared, leading a bunch of dangerous convicts escaped from Impel Down, and he delivered the final blow to Whitebeard, killing his former captain and absorbing (in a yet unexplained way) the power of his Gura Gura no Mi. After conquering most of the former territories of Whitebeard, Teach was recognized by the World Government as one of the Yonko, with a bounty of 2,247,600,000 Belly.
Blackbeard will likely be the final villain in the series, as he acts as a dark counterpart to Luffy, having the same goal of reaching Laugh Tale to become the Pirate King. Both men also belong to the mysterious "D. clan," which is supposed to be the sworn enemy of the Celestial Dragons. Teach's past is still shrouded in mystery, and some fans theorized that Blackbeard might be the son of Rocks D. Xebec, the deceased leader of the Rocks Pirates. Being the only man in history who ever held the powers of two Devil Fruits at the same time, Blackbeard's strength should not be underestimated, especially with the help of the Impel Down convicts, all powerful pirates on their own, who form the backbone of his expanding fleet.
Much of the "Four Emperors Saga" in the manga depicted the rise of a new generation of pirates, including Luffy and the Straw Hat, and their clash with the Yonko. Even if Big Mom and Kaido have been defeated, and perhaps in the future the Yonko will disappear completely, these fearsome individuals have left their mark in history as the most powerful pirates in the world of One Piece.