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.
Things get even worse when the clones start consuming each other to form one powerful entity. In the end, Tanjiro lands a finishing blow to Hantengu's real body. When Hantengu pushes Nezuko into the sunlight, Tanjiro uses Sun Breathing Technique in a moment of desperation and swiftly defeats the Upper Moon.
We first see Doma when he is still the Upper Moon Six while he is in the middle of eating a geisha. Later he becomes even stronger and rises to the position of Upper Moon Two. He dies because of the lethal amount of poison he absorbed through Shinobu Kocho's body followed by Kanao Tsuyuri beheading him.
Muichiro the youngest hashira, killed an upper moon alone ? #demonsla...
Kokushibo was the final Upper-Rank to die during Demon Slayer's "Infinity Castle" arc. Muichiro, Genya, Sanemi Shinazugawa and Gyomei Himejima fought together against Kokushibo, though Muichiro and Genya were no match for him and were killed.
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.
It has been said that no one has been able to kill an Upper Moon in a hundred years, since Upper Moon Six Daki and Gyutaro were killed.
7 Strength: Tengen
Rengoku was an elite fighter with immense strength. He was able to fight Akaza, who was a member of the Upper-Rank Three. Even after sustaining serious injuries, Rengoku still had enough power to hold down Akaza, and was able to send Akaza fling into the forest with a single slash.
After awakening his demon slayer mark, Giyu greatly overpowers Akaza. However, he is able to keep up with the fight only because of Tanjiro. If Giyu had soloed against Akaza, he would have died.
Some of the characters who have faced Yoriichi and survived
This happened due to a treatment that had gone wrong. While he was being treated, Muzan killed the doctor because he was not able to observe any results.
However, unlike many other characters, Nezuko will not die at the end of the series, but will revert to her human form during the Final Battle arc.
Upper-Rank Five: Gyokko
As a fellow artist, Gyokko became distracted by Haganezuka's dedication to sword-polishing and opted to hold off on finishing off a wounded Muichiro. Tokito then manifested his Mark and effortlessly decapitated Gyokko with Mist-Breathing, Seventh Form: Obscuring Clouds.
Shinobu Kocho was the former insect Hashira who played a big role in defeating Doma, the Upper Moon 2, during the Infinity Castle arc. Doma overwhelmed her with his power and Blood Demon Art. However, she decided to let him consume her since she had enough poison in her that would make him vulnerable.
Kaigaku is probably the weakest Upper Moon demon on this list. He served as a replacement to Upper Moon 6, Daki and Gyutaro after they were defeated by members of the Demon Slayer Corps. However, when he fought Zenitsu for the first time, he wasn't accustomed to his newfound powers.
The curse prevents Muzan's name from being spoken aloud, and any who do will meet a horrible demise. One demon, Susamaru, faced this reality when battling Tamayo. Susamaru accidentally shot Muzan's name aloud, attempting to defend his honor with her mind clouded.
Died Together After Confessing Their Love
Mitsuri had already entered the battle with grave injuries, so Obanai forced her onto the sidelines so she wouldn't get hurt anymore. Unfortunately, the Serpent Hashira also succumbed to his injuries. He and Mitsuri confessed their love and died together shortly after.
Tengen Uzui
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.
13th form Tanjiro simply blitzes Akaza. In that form, he's relative to WH Muzan in speed who is faster than all the UMs.
Shinobu Kocho Is the Weakest Hashira
Of the three Hashira who were killed by Upper-Ranks -- Rengoku, Shinobu and Tokito -- Shinobu was the only one who was killed almost instantly when she encountered Doma, Upper-Rank Two.
Gyomei is currently the strongest Hashira.
Demon Slayer's Tengen Uzui is considered to be one of the weakest Hashira due to almost losing this fight, but the fact is that Tengen only looks weak when compared to the most overpowered Hashira.
The Water Hashira, Giyu, survived the "Infinity Castle" arc after fighting beside Tanjiro against Akaza and Muzan.
The demon slayers successfully defeated Muzan.
Nobody replaced Gyokko. We don't really know why, but the Upper Moon Five slot was just never refilled after his death. I'm assuming that Kaigaku was named Upper Moon Six rather than Five because of the fact that he wasn't yet strong enough to move up to that ranking, but that's a good point to raise.