The classic Shonen series One Piece has been running for 25 years, and over the course of this time it has featured a myriad of moments that have changed it forever. Some of these moments have changed how characters viewed the world, some have completely shifted everything fans thought they knew about the series, and the best have done both. This has made it so that the series is almost unrecognizable from where it began in East Blue.
One Piece started as a simple story about a young boy named Luffy who set out to sea in order to become king of the pirates. Along the way, he assembled the Straw Hat crew, who became one of the best found families in all anime and manga. As Luffy and his crew began to encounter more of the world and its injustices, they became a force for freedom and good, which caused them to both become larger figures in the world at large and also to become the enemies of some very powerful organizations. This has led the story to become much more intricate and broad in scope, balancing hundreds of characters, factions, and lore details at once.
10 Arlong Park Walk
Arlong Park was arguably One Piece's best early arc and this moment is a perfect example of why fans view it this way. As Nami breaks down and repeatedly stabs her Arlong Pirate tattoo, Luffy stops her, giving her his hat and assuring her that he and the rest of the crew will take care of her problem. Luffy, Zoro, and Sanji then wordlessly walk to take down Arlong in one of the series' coolest moments. While their actual takedown of Arlong is very important, this moment in the arc best proves that the Straw Hats will do anything to take care of one of their own, a theme that would constantly reemerge as the series continued.
9 Luffy's Execution
Before the Straw Hats leave East Blue and reach the Grand Line, many of their past enemies team up and stage a mock execution for Luffy at the same spot where Gol D. Roger was killed. This plan is of course thwarted by timely intervention from a mysterious figure who would later be revealed to be Luffy's father, One Piece's revolutionary army leader Dragon, but it represents a very important turning point in the series. Not only did it bring the East Blue Saga to a brilliant close, but it also showed that Oda was willing to bring back past villains and teased the power level of some of the major players the Straw Hats would encounter further on in their journey.
8 The Events of the Reverie Are Revealed
The only reason that this event is ranked lower than some of the others on this list is that the full fallout from it hasn't been revealed, but even so, it is easy to see this will affect One Piece going forward. With Sabo escaping to reveal the existence of Imu to One Piece's world as well as the murder and execution of a Celestial Dragon, this is sure to drastically change the entire status quo of the series. In addition, this event has caused the higher echelons of the World Government to become more active than ever before with Imu destroying Lulusia and one of the Five Elders heading to Egghead.
7 Imu Sits on the Throne
Before the events of the Reverie were fully revealed, fans were given a taste of the ultimate head of the World Government when a shadowy figure named Imu sat on the Empty Throne back in chapter 908. This was completely shocking and changed everything that fans thought they knew about One Piece's World Government along with giving rise to a myriad of fan theories about the new character. While the series has revealed a little bit more about Imu in recent chapters, many of the initial mysteries around them remain unsolved, making their first appearance just as impactful now as it was back when it first occurred.
6 Luffy Founds the Straw Hat Grand Fleet
At the end of Dressrosa, Luffy expanded the scope of his captaincy by creating the Straw Hat Grand Fleet, consisting of the many allies he made during his fight against Doflamingo. While the Grand Fleet itself hasn’t done too much since that moment (outside potentially killing a Celestial Dragon at the Reverie), it still represents a major turning point in Luffy’s journey to become the pirate king. All the biggest pirates in One Piece like the four Yonko have commanded major fleets in addition to their core crew. This put Luffy closer to their level as well as served as the foundation of his eventual pirate empire.
5 Luffy Punches a Celestial Dragon
After seeing a Celestial Dragon cruelly try to abduct a mermaid slave and brutally shoot one of Luffy’s friends, the Straw Hat captain broke one of the World Government’s most important laws, socking the pampered brat in the face. Luffy already wasn’t on the best terms with the World Government, due partially to a moment listed later on this list, but this caused the Navy to come down on him in full force. It also directly led to the Strawhats being separated by Kuma and thus to even more series-changing moments listed later. But this was the moment that basically made One Piece's Final War an inevitability, which makes it important enough to include on its own.
4 Usopp Shoots the Flag
Long before the Straw Hats even knew what a Celestial Dragon was, they performed another declaration of war against the World Government just as dramatically. After Robin turned herself into the World Government to avoid hurting her newfound friends because of her bounty, Luffy ordered Usopp to shoot down the flag of the World Government, a bold symbolic gesture that showed there was no enemy the Straw Hats wouldn’t take on to save one of their own. Not only did this show that Luffy was willing to take on the injustices of the World Government directly, but it also proved the full depth of Luffy’s loyalty to his friends.
3 Ace’s Death
The incredibly epic Marineford Arc centers around Luffy’s quest to rescue his brother Ace from the Marines who wish to execute him for being Gol D. Roger’s son. While Luffy tries his hardest and almost succeeds in saving the young pirate, ultimately Ace is killed at the hands of the Admiral Akainu. For a series that had rarely shown Luffy fail and almost never featured a character death outside of flashbacks, this was incredibly shocking both for fans and for Luffy himself. This conclusion to One Piece's best story indicated that the series would be getting a bit more serious in the future and that there were threats the Straw Hats would need to get stronger to face.
2 Gear Fifth
In the climax of the Wano arc, One Piece revealed a piece of information that would change everything fans knew about Luffy’s powers. Instead of possessing the powers of the Gum Gum Fruit, Luffy’s Devil Fruit was actually The Mythical Zoan Human Human Fruit, Model: Nika. Once awakened, the new power of this fruit lets Luffy warp reality to suit his whims, letting him fight in an incredibly cartoonish yet powerful manner. Based on his actions in Egghead, it seems that Luffy will continue to use these powers for the rest of the series, making this moment not just an important lore reveal, but also a major functional change as well.
1 3D 2Y
When the Straw Hats initially separated in Saobody, they said that they would reunite after three days. However, after the overwhelming powers he encountered at Marineford, Luffy realized his crew wasn’t yet ready to enter the New World. Thus, he signaled to his crew that the Straw Hats should train for 2 years apart before reuniting. This led to the series’ famous time skip, effectively separating the series into two halves in fans’ minds. This time skip greatly changed every major character in the series and some important parts of One Piece’s status quo, making it the moment that changed the series the most.
Shockingly, after all the drastic changes the series has undergone, at its core it still feels like the same sort of story. Ultimately, the Straw Hats are still traveling the world fighting injustice wherever they find it, the stakes have just been raised since East Blue. The series will likely undergo even more major changes before it concludes, but as long as One Piece stays true to its core themes, fans will continue to love it.