Summary

Mastery of weapons in One Piece leads to unparalleled strength in characters like Mihawk and Shanks.
Iconic and powerful weapons like Napolean and Kikoku belong to the strongest characters.
The Giant Sword of Elbaf and Onigashima blades may be the strongest in One Piece.

One of the many paths to becoming powerful in One Piece has to do with proficiency in the use of weapons. Many of the strongest characters in the entire series have owed their strength to becoming masters of their weapons, something that has put them on a peerless level where their only company is each other. Whether it’s through the mastery of swords or any other kinds of armament, characters like Mihawk, Shanks, and even Roger are in a league of their own.

Furthermore, the weapons used by these characters are just as iconic and just as strong. Befitting their role in the world, the best weapons tend to belong to the strongest characters in all of One Piece and have no equal in terms of strength or craftsmanship. However, there are some strange weapons in the series whose grade isn’t known and they remain shrouded in mystery, so let’s look at which ones fall under this banner and what their grade could be.

Shanks has been an incredibly important ally to Luffy from the start, but many theories state that he could eventually betray the Straw Hats!

Trafalgar Law’s Cursed Kikoku

Likely Classification: Great Grade Blade

First Appearance
One Piece, Chapter 498, “The Eleven Supernovas”

Story Arc
Sabaody Archipelago

Kikoku is a very mysterious weapon. Although it is confirmed to be a Meito, or ‘named blade’, its exact rank/grade is unknown, prompting many to believe that such a weapon makes sense to be a Great Grade sword. However, what is known is the fact that Kikoku is a Cursed Sword, one of the few confirmed in the series alongside the Kitetsu blades, though the nature of the curse it entails on the user is still a mystery.

People call me the Surgeon of Death.

Law’s sword is quite a bit longer than the standard katanas that are present throughout the series, though it can still be classified as such. The sword itself hasn’t shown any notable traits or feats on its own, but Law has used it very well over the course of the series, most notable of which was when he infused it with his Devil Fruit Awakening to make the blade far longer to send Big Mom down to the base of Wano.

Big Mom’s Napolean Homie

Likely Classification: Supreme Grade

First Appearance
One Piece, Chapter 651, “A Voice From The New World”

Story Arc
Fishman Island

One of the most confusing weapons to grade in the entire series is Napolean, the massive sword that Big Mom uses. This is a special blade since it is a living creature formed from Big Mom mixing a part of her own soul with a sword, turning it into a homie of incredible power. Napolean is one of the strongest homies formed using Big Mom’s Devil Fruit alongside Prometheus, Zeus, and Hera.

Everyone’s got one or two hundred people they want to kill!

Although it is certainly strong enough to be a Supreme Grade Sword and Big Mom’s status as an Emperor of the Sea definitely warrants her having it, many believe that the only reason Napolean is as strong as it is is because of it being made of a fragment of Big Mom’s incredibly powerful soul rather than being a powerful weapon on its own. Even if it isn’t a Meito of any grade, though, Napolean is incredibly powerful.

Eiichiro Oda’s biggest regret might be his handling of Big Mom.

Kaido’s Terrifying Hassaikai Kanabo

Likely Classification: Supreme Grade

First Appearance
One Piece, Chapter 824, “Whim”

Story Arc
Wholecake Island

Just like Napolean, very little is known about the nature of Hassaikai, though a lot of it is speculated on. When in his normal and hybrid forms, this kanabo is Kaido’s main way of dealing damage to his foes, who infuses it with Conqueror’s Haki to make its already incredible power even more deadly to send opponents flying with just one hit. Due to this and Kaido’s role as an Emperor of the Sea, many believe that Hassaikai is a Supreme Grade weapon.

Death is what completes a person!

Moreover, a less-talked-about theory regarding this weapon is that it has taken much of Kaido’s Haki to stain itself black permanently, making it a ‘Black Blade’ too. However, this is highly unlikely since the black color most probably just comes because Hassaikai is completely made out of metal.

The Giant Swords Of Elbaf And Onigashima

Likely Classification: Supreme Grade

First Appearance
One Piece, Chapter 1130, “The Accursed Prince”

Story Arc
Elbaf

Although the Elbaf arc is only in its infancy at the time of writing, the gigantic sword sticking into the land is perhaps the greatest mystery out of them all. Nothing is currently known about this sword, but its titanic size is enough to dwarf even the giants of Elbaf, perhaps hinting at the fact that it may just be the greatest physical weapon in the entire One Piece world.

This is War Land! The mighty kingdom of Elbaf! They say it is the birthplace of war!

Coincidentally, it isn’t the only weapon that’s insanely massive, as the katana buried within the boundaries of Onigashima is similarly sized, perhaps hinting at the fact that giants even bigger than the ones fans have seen once ruled the world. If this is true, then it only makes sense for both the Elbaf and Onigashima blades to be Supreme Grade Swords and, conversely, perhaps the strongest weapons in all of One Piece.