Demon Slayer features demons of many kinds. Throughout the anime, demon slayers are in constant battles to the death with demons who are physically more dominant, faster, and can regenerate. They also possess unique blood demon arts, which makes them highly formidable opponents.
Some demons prove to be particularly challenging to defeat, requiring Tanjiro and his fellow demon slayers to push their skills and body to their limits and also challenge their intellect and ability to read battle situations. Here are some of the hardest demons to kill in Demon Slayer and what makes them so durable.
7 Enmu
Enmu is the antagonist of the Infinite Train Arc and the Lower One Demon and the only Lower Moon Demon to make this list. He was responsible for the numerous deaths and missing persons on the train, which led to the Flame Hashira, Rengoku, being dispatched by the Demon Slayer Corps to investigate the situation. His blood demon art allows him to induce sleep even in the strongest Hashira and enables him to manipulate their dreams.
After Tanjiro decapitates him once and realizes nothing has changed, he discovers that it isn’t his natural body and that he has completely fused with the train. Thanks to the joint effort of Tanjiro and Inosuke, they find out Enmu’s neck hidden near the train engine room. Regardless, it took a lot of effort to hold off his massive body and sever his tough neck.
6 Gyutaro and Daki
These siblings were the Upper Moon Six and had killed the most Hashira before meeting their match at the hands of Tengen, the sound Hashira, Tanjiro, and his friends. Daki’s blood demon art allowed her to control the sentient obi sashes found on her dress, and Gyutaro’s enabled him to send out slashes of poisoned blood from his sickles through the air.
They’re both swift and strong and proved a handful to the demon slayers, particularly because their heads have to be severed off at the same time for them to die, or else they’d just regenerate as if nothing happened. Tengen, Tanjiro, and the rest were pushed to their very limits and even lost body parts and sustained fatal injuries while fighting them.
5 Hantengu
Hantengu is the main antagonist of the sword smith village arc. His powers presented a unique challenge to the demon slayers. Hatengu could split himself into multiple clones with his blood demon art, each with their personality, consciousness, and unique skills. The clones were difficult to distinguish, making it challenging to determine which was the real Hantengu, and the clones will never die as long as the main body was alive—making them play a game where they try to find his main body while being hunted down by his clones.
His ability is activated when Hantengu’s head is severed, his head and body sprouting whole bodies and turning into two separate clones. Those clones can further split into two when they are decapitated as well. Each clone is a manifestation of the different emotions he has felt throughout his life. Discovering Hantengu’s real body was arduous for Tanjiro because he had to use the transparent world technique to find out it was inside his heart.
4 Akaza
He holds the third-highest position, The Upper-Rank Three, in the Twelve Moons. He is very muscular and agile and is a master martial artist. What makes him very hard to kill is none other than his sheer will. He enjoys the thrills of facing formidable opponents in battle. He is so resilient that even after getting his head cut off by Tanjiro, his head refuses to disappear, and his body can still fight on despite being unable to see and hear.
He was so difficult to beat that all efforts to kill him were futile. He decided to end his life after regaining his memories of the past and realizing that he had sullied all the mementos left to him by his wife and father-in-law. He lost the will to fight and realized that he himself was the person he wanted to kill the most.
3 Doma
Doma was the former Upper Six Demon that transformed Gyutaro and Daki into demons, and he now occupies the second position among the twelve moons. His immunity to the wisteria poison is unmatched among all demons in the series. He killed and devoured Shinobu Kocho whole, even though she had absorbed thirty-seven kilograms of wisteria flower poison into her body over the years, about seventy times the lethal amount. However, the wisteria poison took a very long time to weaken him entirely.
Before that, Kanao Tsuyuri tried to cut off his head while he was slightly weakened, but she could not because it was too durable. After being seriously weakened by the poison, it still took the combined effort of Kanao and Inosuke to cut his head off.
2 Kokushibo
The twin brother of the greatest demon slayer ever decided to become a demon in order to thwart the curse that kills people before the age of twenty-five, which comes with activating the demon slayer’s curse. He became a very formidable foe because of his possession of both blood demon art and his moon-breathing techniques. He has also survived decapitation and countless attacks from Hashira, regenerating a new, better, and more monstrous body than he previously had, much to his displeasure.
His katana is made out of his blood, flesh, and bones; he can manipulate the sword and make it grow at will. Because he has a demon slayer mark, he can also read and predict the movement of his opponents, making him a very formidable opponent to face, even for the two strongest Hashira.
1 Kibutsuji Muzan
He is the progenitor of the Demons and the main antagonist of the entire series and is also known as the Demon King. The Twelve Moon demons are an organization sworn to his service and operate under him directly. He is so strong that the other demons tremble at the mention of his name.
His blood demon art allowed him to manipulate his body in ways that have never been seen before, and he can also absorb organic and non-organic materials. To kill Muzan, all his organs must be destroyed simultaneously with a red nichirin sword that can only be awakened with the breath of the sun, and none of the demon slayers could achieve such a feat. In the end the demon slayer corps had to use Muzan's greatest weakness: the sun, to conquer him.