However, when Keizo and Koyuki eventually got killed, Akaza went berserk and ended up killing more than 60 people just with his bare hands.
Akaza fatally wounding the Flame Hashira, Kyojuro Rengoku. Overall Abilities: As the holder of the third highest position in the Twelve Kizuki, Akaza is an extremely powerful demon, having been able to defeat Kyojuro Rengoku and numerous Hashira as well as countless Demon Slayers in the past.
At some point, Daki fought, killed and ate seven Hashira. Two days before Tanjiro Kamado and company infiltrated the Entertainment District, Daki was confronted by Omitsu, the manager of the Kyogoku House, over her mistreatment of the staff.
As Upper Rank Five, Gyokko is more powerful than Gyutaro and Daki, the former having killed 15 Hashira and the latter having killed 7. Gyokko has displayed many impressive feats of strength.
At the end of the day, none of the Hashira could've defeated Akaza – even though a few of them could've succeeded in decapitating him. Akaza proved himself to be too strong to be dragged into sunlight, meaning there'd be no way for any of the Hashira to kill him.
Sound Hashira
He is the fastest Hashira, and the second physically strongest. Obviously, then, Tengen Uzui is rather proud. He is demanding, fussy, boastful, and prone to selfishness. But he is also ultimately kind and caring, with great love for his three wives as well as the other Hashira.
It had been noted that Daki was able to kill and eat seven Hashira in the past, further exemplifying her strength.
Unfortunately, Rengoku was killed by Akaza, the Upper Moon 3. This took place when he, along with Tanjiro, Zenitsu, and Inosuke, boarded the Mugen train to investigate cases of missing people.
However, when Keizo and Koyuki eventually got killed, Akaza went berserk and ended up killing more than 60 people just with his bare hands.
At the age of 12 her success all came to an end when she stabbed the eye of a samurai while her brother was away working. Since her brother wasn't present to protect her, she was then tied up and burned alive and left to die in a ditch. Her brother then carried her burnt body around town searching for help.
Tanjiro decapitates Akaza with the Hinokami Kagura: Setting Sun Transformation. Akaza was bewildered, wondering how Tanjiro did not have any fighting spirit, comparing this feeling to fighting against a plant. He acknowledges that Tanjiro surpassed his speed.
After various battles within the Dimensional Infinity Fortress the remaining Upper Moons are killed by the hands of various Demon Slayers. The last member, Upper Moon Four Nakime, ends up being killed by Muzan Kibutsuji himself to stop the Dimensional Infinity Fortress from being controlled by his enemies.
It affects even the strongest of the Upper Rank demons. This would be effective against Akaza because the only people he refuses to eat are women, since that goes against his morals. Sanemi also has excellent control of his muscles, saving himself from fatal injuries by closing them up himself.
Despite his battle intelligence and the ability to see through enemies with the Transparent World, Obanai doesn't stand against Akaza. He is slower, and his strength is subpar to the demon.
The first of the Twelve Kizuki that was encountered in the series was the former Lower Rank Six, Kyogai, who is slain in battle by Tanjiro Kamado.
Some of the characters who have faced Yoriichi and survived
While he was being treated, Muzan killed the doctor because he was not able to observe any results. This turned him into one of the strongest beings that could defeat multiple Hashiras in one go.
Fortunately, Zenitsu was able to single handedly beat the Upper Moon 6. Not only did he defeat the demon, he also created a seventh form called the Flaming Thunder God. These are the demons who have been given the title of Upper Moon 6 in Demon Slayer.
As for the "last ever Hashira"...that would be Shinazugawa-san as well as Tomioka-san.
2) Rengoku
However, Rengoku was forced to face off against Akaza who was Upper Moon 3. The Flame Hashira carried out his duties until his death as he did not let his comrades get injured.
So far, the only Hashira we meet in the Demon Slayer series who has died is the Flame Hashira Kyōjurō Rengoku. Although he isn't the first of the elite squad to get to know Tanjiro, he is one of the first, and he accepts Nezuko and won't kill her despite the fact that she's a demon.
In terms of physical strength, Tengen Uzui is far from being the weakest Hashira. While his feats throughout the Daki and Gyutaro battles certainly displayed this, there's additional evidence to show that he's not the weakest Hashira.
As it turns out, Tanjiro has received a few promotions during his service. However, saying that Tanjiro has become a Kanoe doesn't mean much on its own. The Corps' ranks and functions are fairly straightforward.
1) Shinobu Kocho
The Insect Pillar of Demon Slayer Corps, Shinobu is undeniably the smartest individual. She might not be physically stronger than others, but her intelligence is what kept her going.