The 9 Pillars of Demon Slayer: Kimetsu no Yaiba are quite different from each other in the aspects of personality, strength, Breathing Techniques, and speed. Each possesses a set of unique skills that make them effective combatants on the battlefield.
Whereas only strength and endurance are not the key to victory against anomalously strong demons, a Demon Slayer must also have Tactical Intelligence to turn the tides in their favor.
Luckily the Hashiras are blessed with such abilities and are formidable combatants. These Pillars could be classified based on their strength. The strongest Pillar in the Demon Slayer Corps is Gyomei Himejima. Gyomei is a Pillar of Stone Breathing, which is considered the hardest Breathing technique that one could master.
Likewise, the Upper Demon Moons are also powerful and could dominate their opponents in a battle with their immense strength and their Blood Demon Art. Kokushibo is the Upper-Rank One Demon and also is the right-hand man of Muzan Kibutsuji. If Gyomei goes against Kokushibo, would he be able to defeat him or would this be his last fight?
Note: This article is subjective and reflects the writer's views.
Is Kokushibo the most powerful demon after Muzan in Demon Slayer?
Kokushibo is the most terrifying demon who holds the top position in the 12 Demon Moons. Surprisingly in his human days, he was the brother of the legendary warrior Yoriichi Tsugikuni, who was the progenitor of all Demon Slayers and the Breathing Technique.
Being incapable of learning the Sun Breathing from his brother, he developed his own Breathing Technique called the Moon Breathing. After becoming a demon he enhanced his Breathing Technique with his Blood Demon Art over the centuries.
His Moon Breathing allows him to create multiple crescent-shaped katana out of his flesh. Merging his swordsmanship with Blood Demon Art, he became a more formidable demon next to Muzan.
Can Gyomei defeat kokushibo?
The most likely character to go against Kokushibo is Gyomei Himejima. Gyomei, despite being blind, is freakishly strong and a skilled combatant who is all about his monstrous strength, tremendous speed and reflexes. He mastered Stone Breathing which is considered to be the strongest Breathing Technique subsequent to Sun Breathing.
Aside from these skills, in the Infinity castle arc, Gyomei was able to hold his own against Kokushibo while fighting him alongside Sanemi Shinazugawa. Kokushibo acknowledges that throughout the centuries he has fought numerous swordsmen, but no one was as strong as Gyomei.
Eventually, Kokushibo was killed by the duo: Sanemi and Gyomei. Even if Gyomei had gone solo against Kokushibo he could defeat the latter by awakening his Demon Slayer mark.