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In the world of One Piece, there are many different Devil Fruits that belong to one of three categories; Paramecia, Logia, or Zoan types. With the latter, the user can turn into different kinds of animals, though there are also far rarer versions of Zoan fruits that allow the transformation into extinct animals or, most interestingly, even mythical creatures and Gods.
These are called Mythical Zoan Devil Fruits, and they tend to be the strongest Devil Fruits in all of One Piece. As such, some of the most powerful characters in the setting are users of Mythical Zoan fruits, using which they have some insanely powerful attacks.
Yamato's Namuji Glacier Fang Matched Kaido
Debut Arc: Wano
Yamato debuted in the Wano arc and proved to be an incredibly powerful character, especially in their battle with Kaido. They even managed to match the World's Strongest Creature for quite a while. In this fight, one of the most powerful moves Yamato used was a direct attack of their incredible Mythical Zoan fruit.
The Namuji Glacier Fang allowed Yamato to form many icicles around their body and then fire off an icey breath attack that was so powerful that it matched Kaido's legendary Blast Breath, confirming Yamato as an exceptionally powerful character with a very strong Devil Fruit.
Sengoku's Shockwaves Subdued The Tremor Fruit
Debut Arc: Marineford
It's no secret that Whitebeard's Gura Gura no Mi is the most powerful Devil Fruit in the entire series, as it's capable of destroying the entire world. At the same time, Sengoku is the user of the legendary Hito Hito no Mi, Model: Daibutsu Mythical Zoan Devil Fruit, which has the power to create immensely powerful shockwaves.
Although we never got a named attack from the former Fleet Admiral, the shockwaves that he created were powerful enough to almost entirely stop the tremors created by the Gura Gura no Mi. This was after Blackbeard had stolen the fruit from Newgate's body, making Sengoku one of the strongest characters of the old era.
Kaido's Flame Dragon Torch Made Him Untouchable
Debut Arc: Wano
To this day, Kaido is still remembered as perhaps the greatest foe that Luffy has ever faced. Many One Piece fans tend to keep him at the top of the ranking due to his insane feats. Although he showed quite a few incredible techniques in his many fights, such as the Thunder Bagua or Blast Breath, his greatest attack was his insane Flame Dragon Torch.
Using the fire-breathing abilities of his Devil Fruit, Kaido proceeded to cover his entire draconic body in fire hotter than the one he uses with his Blast Breath, which is a notable distinction since Blast Breath can destroy entire mountains. With the Flame Dragon Torch, Kaido grows in size exponentially and gains a massive boost in his already incredible speed and strength.
Thorheim Is One Of Loki's Strongest Attacks
Debut Arc: Elbaf
The Elbaf arc revealed the existence of the legendary Nidhogg fruit, which is currently in the possession of Prince Loki of Elbaf. Through this Mythical Zoan fruit, Loki transforms into a towering dragon that is the size of an island, making his strength some of the fiercest in the entire One Piece setting.
In his brief altercation against Imu, Loki used a breath attack similar to Kaido's Blast Breath called Thorheim, only Thorheim was far larger and way more powerful. The size of this attack and its blast radius were so huge that even Imu was unable to escape it, proving just how formidable the strength of Loki is within his Nidhogg form, since it even significantly damaged the villain.
Imu's Omen/Maki Is A Terrifying Mystery
Debut Arc: Elbaf
Few were expecting Imu to make his full debut in the Elbaf arc, but when he did, the entire power scaling of the series was sent into an uproar since his strength was completely off the charts. One of the biggest reasons for this legendary power was Imu's mysterious Omen/Maki ability.
Although very little is known of it right now, it can be seen that, through the Omen of his Devil Fruit, Imu can greatly empower anyone of his choosing to an unprecedented degree, not only increasing their overall strength, but even further bolstering their abilities. This is a power that's even greater than his Domi Reversi, and many have theorized that Maki is an evil version of Haki.
The Bajrang Gun Is The Strongest Mythical Zoan Attack
Debut Arc: Wano
In his Gear 5 state, Luffy gains access to minor reality-warping powers which allow him to do many fantastical things. One of the most apparent is his ability to change his size at will, which he did in every single usage of his legendary Gear 5 state. The strongest attack that Luffy can do while in this form is his Bajrang Gun.
Much like Loki's Thorheim, part of the reason why Bajrang Gun is arguably the strongest attack in all of One Piece is because of its sheer size, making it impossible for anyone to dodge effectively. By increasing the size of his fist to that of an entire island and imbuing it with Advanced Conqueror's and Advanced Armament Haki, Luffy then unleashes an attack with unparalleled destructive force.
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