Yamato's gender

In One Piece, Yamato identifies himself as Kozuki Oden, considers himself Kaido's son, not a daughter, and even uses male pronouns to call himself in Japanese.
Like Kikunojo, Yamato's depiction of gender itself is not the problem, but rather a subtle, elegant depiction of transgenderism, at least when compared to One Piece's previous depictions of transgender characters. . Most of the controversy surrounding Yamato stems from general confusion and mixed reactions from fans.
The animation of Gear 5 in the anime

Luffy's newest form – Gear 5 received mixed responses upon its debut in the anime. While the reveal in the manga was also met with some skepticism, Gear 5's debut in the anime sparked countless fierce debates due to its absurdity.
Many people believe that Gear 5 is ruining One Piece and will lose the seriousness of future battles. Others believe that the Gear 5's reality-bending power is simply too strong. The Egghead arc proved that Gear 5 can be funny while still giving fans equally great, intense battles, and One Piece still has many formidable opponents that can match Gear 5.
Robin's skin tone changes after the timeskip

Along with the newly improved animation, One Piece's timeskip also saw many members of the Straw Hat crew redesigned. One particular change that fans are still quite upset about to this day is Robin's lighter skin tone. Robin, along with Zoro and Usopp, were visibly bleached after the time skip, and it remains unclear why.
Regardless of the reason, this change remains a point of contention even years later, with many fans wanting Robin to return to her old iconic look.
Fan service xung quanh Jewelry Bonney

One Piece's Egghead arc has seen Jewelry Bonney thrust into the spotlight, although some recent revelations about her have caused some controversy. One Piece chapter 1098 confirms that Bonney is in fact only 12 years old, having used her devil fruit powers to appear more mature.
This revelation about Bonney's real age made some images of her sensitive, making many fans feel uncomfortable. Even the beginning of the Egghead arc portrays Bonney as quite provocative and scenes like Blackbeard asking Bonney to become his woman are disturbing.
The power of S-Snake affects adults

Seraphim is one of One Piece's greatest new additions to the saga. In the case of S-Snake, Boa Hancock's clone, she also possesses the power of the Mero Mero no mi devil fruit. However, the capabilities of this power used by the childish-looking S-Snake have caused quite a bit of controversy, especially since they seem to have good effects even on adults.
The SBS arc in episode 106 of One Piece clarified that the Mero Mero fruit's power even works when people think the user is cute.
Pell's “death”.

One controversial decision that certainly haunts One Piece fans to this day is Pell's death. We saw Pell grab a bomb and then fly into the air to save Alabasta. In the anime everyone thought Pell would die but it turned out later that the truth was revealed that he was still alive.
This detail is one of the biggest reasons why many fans don't believe a character is truly dead unless they see the body or the character's funeral, or both. Even worse, One Piece continues to do so with many characters such as Igaram, Sabo and most recently Dr. Vegapunk.
Vander Decken's obsession with Shirahoshi

During the Isle of Man arc, there was Vander Decken's decades-long inappropriate obsession with Shirahoshi, which began when the mermaid princess was six years old while Decken was 25 years old.
Not only did Decken track Shirahoshi with his devil fruit powers, but he also tried to take the princess's life when she did not agree to marry him in the present day, when she was only sixteen years old.
Absalom's inappropriate behavior towards Nami

In the Thriller Bark arc, Absalom abused his invisibility Devil Fruit power to peek at Nami. His behavior towards Nami could easily be classified as harassment. Not only did he violate Nami's privacy, without consent he grabbed her wrist and also pinned her against the wall before declaring her his bride.
Absalom then kidnaps Nami and tries to kiss her while she is unconscious. Absalom's actions are generally much more sinister and ferocious than any other actions in One Piece.
Kamabakka Kingdom's treatment of Sanji

Although Bon Clay, Ivankov, and the okama of Impel Down serve as exemplary representatives of Japanese okama culture, as well as the transgender community, the depiction of the kingdom of Kamabakka during the timeskip is unsatisfactory. , especially their behavior towards Sanji.
When Sanji arrived at Kamabakka kingdom, the okama chased the chef to force him to become okama. Sanji described the place and his time there as a living hell.
Whitebeard's original Jolly Roger flag

Whitebeard's Jolly Roger wasn't always the cross shape that fans know today. The original symbol of the Whitebeard Pirates, as well as the symbol tattoo on Ace's back, used to be a swastika. It was changed at Oda's editor's request, to avoid controversy when One Piece began to gain popularity outside of Japan.
Although the swastika is often associated with luck and auspiciousness in Southeast Asia, the symbol has largely negative connotations in the West, which is why it was changed.