In the world of One Piece, alliances are often formed when the goals of certain organizations align and the rewards benefit both the parties. Although not exclusive to pirates, it is most commonly seen among them, and on a few occasions, among the Marines as well. Most of the pirate alliances in the series are said to end in betrayal, which isn't surprising since that's the way of a pirate.
Over the years, we've seen lots of alliances get created to take down enemies such as the Yonko, or even the World Government. Here are the 10 most powerful alliances that we've seen in the series so far.
10 Impel Down Alliance
The Impel Down alliance was created during the major breakout that ensued right before the Paramount War arc in One Piece. This alliance was led by none other than Monkey D. Luffy, with powerful allies such as Ivankov, Crocodile, Jinbei, and others such as Buggy, and some Baroque Works members also being a part of it.
Thanks to their unstoppable strength, they successfully broke free out of the impregnable prison and went on to wreak havoc on Marineford shortly afterward. While this alliance was a bit short-lived, it certainly shook the world to its very core.
With the Worst Generation taking the stage after the time-skip, it wasn't hard to guess that their targets would be the Yonko of the Sea. Just as Luffy and Law targeted Kaido, Kid, Hawkins, and Apoo had something else in their minds and their target was Red-Hair Shanks.
Unfortunately, this alliance didn't last long as Apoo was actually working for Kaido already and set them up to get ambushed by the Yonko. They were utterly defeated by Kaido, with Hawkins bring forced to join the crew and Kid being thrown into a prison cell.
8 Strawhat-Firetank Alliance
Established at Whole Cake Island, this alliance was formed at the suggestion of Jinbei, who recommended to Luffy to join hands with Capone Bege. Together, they planned to take down Yonko Big Mom and save the Vinsmoke Family in the process.
Comprising of strong members, such as Luffy, Jinbei, Sanji, Nami, and Bege among others, this alliance did more than enough to turn the tables on the Big Mom Pirates and almost succeeded in taking her down as well. Although their plan failed, Big Mom's reputation was severely harmed as Luffy and Bege managed to escape alive, albeit with some sacrifices.
7 Strawhat-Heart Alliance
This alliance was born at the restricted island, known as Punk Hazard and was masterminded by the Surgeon of Death, Trafalgar Law. Created with the intention of taking down Yonko Kaido, the Strawhat-Heart alliance dealt a significant blow to the Yonko's SMILE trade by destroying the SAD factory and breaking the gears of the era in the process.
Furthermore, the Strawhat-Heart alliance then traveled to Dressrosa, where they put another dent in Kaido's plans by taking down the Joker, Donquixote Doflamingo. This Pirate alliance was bolstered with more members later on and remains to be one of the strongest alliances in the series to date.
6 Pirate-Ninja-Mink-Samurai Alliance
Upon recruiting more members, the Strawhat-Heart alliance was transformed into the Pirate-Ninja-Mink-Samurai alliance. The already strong alliance that was actively targeting Yonko Kaido was joined by the Samurai and the Ninja of Wano Country, and also the Mink Tribe of Zou.
At Wano, they've caused a huge ruckus already and they're just hours away from setting their final plan in motion and engaging into a fight against the Beasts Pirates at Onigashima. With enough power to bring down a Yonko, it goes without saying that this alliance is one of the strongest there ever was.
5 Marines and Shichibukai Alliance
To stop pirates to some extent, the Marines, at one point, used to recruit more Pirates to do their job for them! Bizarre as it may sound, it actually worked quite well for both sides as the Marines gained powerful allies and the pirates gained immunity from being hunted down. These pirates were known as the Seven Warlords of the Sea.
In conjunction with the Marines, the Warlords were used to counter a Yonko crew in terms of power. Although we didn't get to see them in action often, Marineford was a fine display of what this alliance could achieve when it worked together. Needless to say, the results weren't disappointing.
4 The Golden Lion Armada
Led by none other than the Captain of the Golden Lion Pirates and a former member of the Rocks Pirates, Shiki, the Golden Lion Armada was the largest pirate alliance prior to the Great Pirate Era in One Piece. Along with the Whitebeard and Roger Pirates, they ruled the seas quite comfortably.
During the Edd War, this alliance was decimated due to an unknown storm that hit them head-on and left disastrous repercussions. After Shiki's capture at Marineford, the fate of the members of this alliance was left up in the air.
3 The Whitebeard Pirates Allies
The Whitebeard Pirates, also known as the mightiest pirate crew in the Great Pirate Era, were led by Yonko, Edward Newgate, also known as Whitebeard. Under Whitebeard were 16 Division Commanders each of which commended 100 men. The total strength of this crew was around 1600 men strong, but that's not all.
Several crews of the New World had also allied with the Whitebeard Pirates, all of which were led by infamous pirates across the New World. Although the exact count of the fleet isn't known, it is said that the alliance had 43 subordinate crews in the Paramount War. Undoubtedly, this was a massive alliance that sent shivers down the spine of the World Government.
2 Marines-Roger Pirates Alliance
38 years prior to the current events in the world of One Piece, a mysterious event known as the 'God Valley Incident' took place somewhere in the New World. The Rocks Pirates, who had grasped the age by the scruff of its neck, were completely destroyed at God Valley. According to Sengoku, the Marines, specifically, Garp, teamed up with the Roger Pirates to decimate the Rocks Pirates once and for all. Rocks was apparently killed in this fight, while his young crewmates survived only to gain more power and lead the upcoming generation by becoming the Yonko.
Corrupt as the World Government is, they gave the entire credit to Garp, which led to him getting the title of 'Garp the Hero'. Although it is unclear how they defeated Rocks, the alliance certainly is one of the strongest that the One Piece world has ever seen.
1 Big Mom-Kaido Alliance
Unarguably the strongest alliance to date, Big Mom-Kaido alliance was created recently at Wano Country, where the two, after fighting continuously for 12 hours, decided to join forces and completely wreck the entire world, following which they would try to kill each other again. This is, in fact, much in line with how the Rocks Pirates operated back in the day. As explained by Sengoku, this alliance is enough to send the world in a state of chaos, while Garp believes nobody is capable of stopping them.
Not only does this alliance have two Yonko at the helm, but they also have some incredibly powerful subordinates, such as The Calamities, the Numbers, and half of the Big Mom Pirates as well.