Every faction in the One Piece universe needs a strong swordsman to represent them. Given this, the straw hats are no different. Roronoa Zoro dreams of one day defeating Dracule Mihawk and claiming the title of the world’s strongest swordsman.
This is no easy task as Mihawk is a man who has shown himself to be equal to that of some of the most powerful pirates on the seas, the Yonko. Naturally then, Roronoa Zoro must hone his skills and develop strong attacks to one day reach the level he so desperately craves. Zoro has chosen to walk the path of Asura in order to achieve his dreams, this path, though harsh, will make him one of the strongest. These are some of the strongest techniques he's used so far during One Piece:
10 TWO SWORD STYLE: TORO SAMON
After training under the tutelage of the greatest swordsman in the world over the two-year time skip, Zoro added new attacks to his arsenal. This specific move sees him combine a couple of his previous moves: Nigiri, Toro, and Samon. Zoro assumes a stance with two of his swords held horizontally across his body, before launching himself at his opponent at an insane speed. He then launches a diagonal air slash at the target. This is first seen in the Wano arc against the supernova and member of the worst generation Basil ‘The Magician’ Hawkins. Zoro used this attack to destroy Basil's straw monster to allow himself and Luffy to evade Hawkin’s capture attempts.
9 ASURA: ONE MIST SILVER
After receiving a ravenous onslaught from Kaku, along with his disrespectful taunts, Zoro begins to emit a demonic aura. As he channels it more and more, his surrounding becomes darker and the atmosphere, more ominous. Zoro raises two swords above shoulder height with his final sword in his mouth. As he continues to channel Asura, four more arms and two heads appear out of nowhere. Zoro then rushes towards his opponent before slashing them with all nine swords at once. This move easily dispersed Kaku's strongest attack before finishing him off.
8 GREAT DRAGON SHOCK
This move is featured in one of Zoro's most badass moments. This is, of course, the moment in which he cuts down Monet in her logia form, without the use of armament haki. He manages to scare her into submission via the intensity of his aura and immense blood lust. To use this technique, Zoro runs up to an opponent with one sword in hand before grabbing it with both hands, then making a vertical slash right down the center of his opponent. When used against Monet, she was completely split in half and temporarily lost the ability to reform her logia body.
7 UL-TORA GARI ULTRA TIGER HUNT
This attack is a much stronger version of Zoro's previous Tora Gari, he developed this over the two-year time skip while training on Kuraigana island. We first see it used on thriller bark to deal damage to a rampaging dragon. When using this technique, Zoro assumes a wide stance before placing Wado Ichimonji in his hand, then stretches his arms out horizontally. He then raises them above his head before placing them behind his back.
After completing this stance, a tiger-like aura can be seen behind Zoro, he then swings all swords at his opponent. This attack was strong enough to almost completely render Dragon number thirteen unconscious.
6 THREE SWORDSTLE SECRET SKILL: CROSSROADS OF SIX PATHS
This is a sword technique that allows Zoro to unleash six powerful, curved air slashes at once. This was seen when the Straw hat pirates were heading to Fishman island and encountered the kraken, Surume. Zoro once again places Wado Ichimongi in his mouth and it begins to glow. As he begins to unsheathe his remaining swords, they also begin to glow brightly. He then performs a quick draw before twisting sharply to provide a curved effect to each of the slashes. This attack completely demolishes one of the giant tentacles of the Kraken and leaves it in fear.
5 PURGATORY ONIGIRI
Another upgraded sword technique that Roronoa developed during his training and debuted during Fishman Island. This is an upgrade on one of his most favored moves, Oni Giri. This purgatory version is far more potent and put Hyouzou out of commission after a single attempt. To perform this technique, Zoro first faces away from his opponent before placing Wado Ichimonji in his mouth and placing his arms diagonally across his chest while wielding his swords. He then hunches over before turning and launching himself at his opponent quickly. To top this off, he unleashes a three-point diagonal slash that generates incredible power. This was more than enough to break all of Hyouzou's swords easily.
4 ONE SWORD STYLE: DEATH-LION'S SONG
A classic sword technique that has to be in any respectable swordsman's repertoire. Shi Shishi Sonson is a quick draw and re-sheath technique that hits an opponent before they can even react. Despite its basis as a speed attack, the destructive force is definitely something to write home about.
This easily decapitated Dragon number thirteen during its clash with Zoro. When using this technique, Zoro first steadies himself and ensures his body comes to a complete standstill. As he begins to unsheathe his sword, he also closes his eye before quickly slashing and then resheathing his blade.
3 GREAT DRAGON TWISTER
This is easily one of the strongest techniques Zoro has used since the two-year time skip. Before, he always struggled with projectile type attacks but, after training, he managed to overcome that previous limitation. This leads to one of his most glorious moments while on Fishman Island. Zoro stretches both arms out horizontally to his right, while Wado Ichimonji also faces right while in his mouth. As a dragon’s aura begins to appear behind him, Zoro spins rapidly creating a whirlwind type slash. This whirlwind continues expanding, even after the initial slash, and keeps going until it slashes everything Zoro desires.
2 1080 POUND CANNON
When fighting Pica, Zoro quickly realized he needed to hastily reduce the size of the humongous rock that Pica assimilated himself into. To do this, he used a superior version of an attack that was once one of his strongest. For this version, Zoro jumps into the air and, while air born, he raises two swords above shoulder height as he begins to twist his body, before unleashing three curved, air slashes. These three slashes fly through the air and as they eventually combine into one giant slash before striking the target. This was strong enough to destroy a significant portion of Pica’s rock body while doing damage to his 'real' body as well.
1 THREE SWORD STYLE SECRET SKILL: BILLION-FOLD WORLD TRICHILIOCOSM
This is Zoro's strongest attack and was first used back in Dressrosa in the lead up to Pica's defeat. Zoro, after being propelled in the air at an insane speed, begins to spin the swords in arms around, interchanging them between hands, as they gather more and more momentum. He then releases slash after slash with deadly accuracy, speed, and force. This attack is strong enough to cut through Pica's reinforced rock body as if it were a knife going through butter. The potency of this attack shocked every single bystander who witnessed it.