Here’s the list about the strongest Armament Haki (Busoshoku Haki) Users. Of course the list contains only those characters who have already shown this ability:
10 – FUJITORA/ KATAKURI/ 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.
9 – HYOGORO / KAWAMATSU / SENTOMARU
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.
Kawamatsu is masterful in Busoshoku Haki. This is shown when he performed an attack named Yagura Ryuo which repelled several Beasts Pirates charging toward him without direct contact.
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.