Armament Haki (Busoshoku Haki) is a form of Haki that allows the user to use their spirit to create, in essence, an invisible armor around themselves.
A heavy concentration (or coating) of this Haki can be used to harden parts of one’s body, turning the area black, thus making the user denser and more formidable, and giving their attacks greater power. As demonstrated with Vergo and later Pica, it is possible for one to coat their entire body in Busoshoku Haki.
Notably, this form of Haki can be used to injure Logia Devil Fruit users and allows the user to defend against attacks that would otherwise cause them harm.
An Advanced application of Busoshoku Haki allows the user to emit the armament to a short distance. This was first demonstrated by Sentomaru in Chapter 511.
Here’s the list about the strongest Armament Haki Users. Of course the list contains only those characters who have already shown this ability:
10 – FUJITORA/KATAKURI//LUFFY/SABO
Fujitora could clash head on physically with Sabo, a Logia-class Devil Fruit user and also a proficient Busoushoku Haki user, demonstrating an extremely high level of skill in Busoshoku Haki. He could focus strong concentration of Busoshoku Haki into his sword, turning it obsidian black and making it strong enough to defend against the razor sharp threads of the Birdcage, which can slice cannonballs and buildings with great ease.
Katakuri is an extremely powerful Busoshoku Haki user, as shown when he imbued his mochi leg with it in order to bludgeon and injure Luffy. His Haki enhanced strikes are powerful enough to counter and overpower Luffy’s own Haki enhanced attacks, and he has boasted that his Busoshoku Haki is superior to Luffy’s. When his Haki is compressed and focused when performing his Zan Giri Mochi attack, Katakuri’s Haki becomes flame-shaped like Big Mom’s Haki and Luffy’s Haki when he uses Gear Fourth and the luster of it is light blue unlike Luffy’s pinkish red.
Sabo has shown incredible mastery of Busoshoku Haki, which he can imbue into his arm or his pipe. His Busoshoku Haki is strong enough to shatter Burgess’s Haki infused right arm armor, as well as Diamante’s sword. His mastery of Busoushoku Haki is superior to Bastille’s, as seen when the Vice Admiral attempted to cut him down with Haki enhanced sword strikes; not only did Sabo manage to block his Same-kiri Bocho, he even managed to destroy the entire blade with relative ease.
Luffy has gained an extremely high mastery of Busoshoku Haki. When his Busoshoku Haki is further compressed and focused in his Boundman and Tankman form, his Haki is fortified to the point that powerful Busoshoku masters such as Doflamingo, Cracker, and Katakuri could not fully defend against his attacks.
Luffy is currently attempting to learn an advanced application of Busoshoku that will allow him to emit his Haki a short distance without a medium.
Sentomaru can use Busoshoku Haki to enhance his attacks. His control is such that he can not only strike Devil Fruit users and cause them harm by bypassing their defenses, but do so without actually making physical contact. He claims to have the “world’s greatest defense”, shown when Luffy could not land even a single punch on him.
Sentomaru can use Busoshoku Haki at an advanced level that allows him to emit his armament a short distance without a medium.
8 – HYOGORO
Hyogoro of the Flower, currently better known as Grandpa Hyo, is a prisoner in the Udon region of Wano Country. Twenty years ago, he was the most famous yakuza boss in Wano.
Hyogoro is an extremely skilled and experienced Busoshoku Haki user, which is called “Ryuo” in Wano. He can harden parts of his body and can utilize an advanced application of Busoshoku Haki that allows him to emit his Haki a short distance without a medium. It is strong enough to strike down a Gifter without touching him.
7 – KIZARU
Kizaru was seen using an advanced level of Busoshoku Haki to negate Whitebeard’s attempt to destroy the execution platform, by creating, with his fellow admirals, a shield combination of their three Haki.
6 – KUZAN
During the Battle of Marineford, Kuzan was seen using an advanced level Busoshoku Haki just like Kizaru.
5 – AKAINU
Just like Kizaru and Kuzan, Akainu was seen using Advanced Busoshoku Haki during the Battle of Marineford.
4 – SHANKS
Shanks has great mastery over Busoshoku Haki, as shown during the Battle of Marineford, with his Haki infused sword he easily blocked Akainu’s magma enhanced punch that is powerful enough to burn the strongest enemies such as Ace, Jinbe, and even the Yonko Whitebeard.
3 – BIG MOM
Big Mom has immense mastery of Busoshoku Haki. By hardening her arm, she could easily block Luffy’s Gear Fourth Kong Gun, a tremendous feat as Luffy’s Kong Gun is powerful enough to break through powerful Haki based defenses of highly skilled Busoshoku Haki users such as Doflamingo, Cracker and Katakuri.
2 – SILVERS RAYLEIGH
Rayleigh has an extremely high level of skill in Busoshoku Haki, allowing him to effectively bypass the powers of a Devil Fruit user and touching the “substantial body” beneath whatever protection the fruit provides as seen when he used Busoshoku Haki to kick and redirect an attack from Admiral Kizaru. Rayleigh’s immense proficiency in Busoushoku Haki allows him to use it for devastating offense. Furthermore, Rayleigh can utilize an advanced application of Busoshoku which enables him to emit his Haki a short distance without a medium.
1 – MONKEY D. GARP
He demonstrates extremely proficient skill in Busoshoku Haki, being able to injure Luffy several times, bypassing his rubber body. He could harden his fist and turned it obsidian black, allowing him to counter and even crush Chinjao’s Haki-enhanced drill shaped head 30 years ago, proving his superior mastery compared to Chinjao, who himself is a powerful expert Busoushoku Haki user in his own right. During the Battle of Marineford, he managed to punch and hurt Marco despite the latter being in his regenerative phoenix form.