As a proper shonen action anime, Demon Slayer is packed with deadly and exciting villains for heroes like Tanjiro Kamado to fight. These villains — nearly all of them demons — vary a great deal in their powers, abilities, appearance, and backstories. They also vary somewhat in how evil they are, since a few demons are either relatively tame or never had a chance to prove how wicked and horrible they are.
Regardless of powers and abilities, some Demon Slayer villains are much crueler and more vicious than others, meaning some have the true heart of a villain while others are just going through the motions as antagonists for the demon slayers to fight. True acts of evil are nearly impossible to forgive or forget, such as abusing the weak, turning friends against each other, or creating sorrow and misery for the fun of it.
10 The Swamp Demon Regularly Preyed on Teenage Girls
The swamp demon was the least evil of Demon Slayer's most wicked villains, making his debut fairly early in the series. At the time, Tanjiro only had his little sister Nezuko to back him up, so it was easy for the swamp demon to split into three bodies to outnumber Tanjiro's tiny team. Fortunately, Tanjiro's Water Breathing was the perfect style to finish him off.
As for his evil deeds, the swamp demon regularly preyed on teenage girls, finding them to be the most delicious prey of all. It's usually the cruelest and most twisted demons who pursue particular prey like that, and he terrorized an entire town for quite some time with those swampy abductions until Tanjiro arrived to save the day.
9 Akaza Killed Kyojuro Rengoku in Cold Blood
It's been argued that Akaza was never truly evil, despite his immense power as the Upper Moon 3. True, he had a sense of honor while fighting Kyojuro Rengoku the Flame Hashira, but he still killed Kyojuro in cold blood, and he was too late to save Enmu anyhow. Akaza seemingly challenged Kyojuro to a fight just for the sake of it.
Akaza repeatedly offered to turn Kyojuro into a demon, pressuring the honorable Flame Hashira into abandoning his humanity and principles, an insidious offer for any demon to make. Kyojuro refused, so Akaza simply killed him with a fist through Kyojuro's gut. Then Akaza fled, and now he aims to kill Tanjiro Kamado next, as if killing Kyojuro wasn't bad enough.
8 The Hand Demon Sought Out and Killed Sakonji's Students
The so-called hand demon was the first noteworthy demon whom Tanjiro ever killed in Demon Slayer's anime, and it was actually personal for both of them. While Tanjiro has few shonen-style mentors, he did train with Sakonji Urokodaki, who captured the hand demon and placed that creature in that final selection training ground.
Ever since then, the hand demon has sought out and personally dispatched Sakonji's students to get back at the demon slayer who humiliated him, and that's a pretty wicked act for any demon. However, being his sympathetic self, Tanjiro still saw and appreciated the hand demon's humanity despite it all, and he wept as the massive hand demon finally died.
7 Gyutaro Tormented Tanjiro to Defend His Little Sister
Gyutaro was the true Upper Moon 6, a terrifyingly powerful demon who has killed multiple Hashira over the last several decades. He was even stronger thanks to his bond with his little sister Daki, since neither of them will die to decapitation while the other has their head. As for his personality, Gyutaro is distinctly vile and aggressive.
Gyutaro fought hard to protect his little sister, which is the only non-evil thing he ever did. As a human living on the fringes of society, Gyutaro often attacked people, and that didn't win over the hearts of Demon Slayer fans. Then, in the present, Gyutaro made a sport of tormenting and hurting Tanjiro during their fight, and he even mocked Tanjiro for apparently failing to protect his own little sister.
6 Daki Lured People to Their Deaths in Her Oiran Disguise
The other half of the Upper Moon 6, the vicious himedere Daki, hid in plain sight in the entertainment district, where she passed herself off as an oiran. Daki, like her brother, suffered from poverty and hardship growing up, and it made her desperate for validation. After nearly dying, she became a demon, and realizing her dreams of being strong and beautiful for all to see.
Daki didn't have Rui's spider theme, but she did behave like a spider, using the entire entertainment district like her web to catch unsuspecting prey and store them in her lair for later consumption. Daki was also rather abusive even in her oiran disguise, as Zenitsu saw for himself in his own disguise before the battle started.
5 Rui Abused His Found Family
Rui held the rank of Lower Moon 5, though he might have risen in the ranks if he made the right moves. No matter his placement among the Kizuki, though, Rui still ranks in the middle among Demon Slayer's evilest villains thanks to his abusive ways toward the found family he built.
Rui gathered other people and turned them into demons to join his found family, with him being one of the sons. However, demons are not too prone to healthy family dynamics, least of all Rui, who regularly mistreated most other family members with his words and violence alike. The exception was the nightmarish spider father, who commanded Rui's respect as a powerful warrior.
4 Doma Happily Killed Kanae Kocho
At a glance, the Upper Moon 2 may not seem that bad, but he was actually one of the evilest demons to ever serve Muzan Kibutsuji — or at least, he is the least capable of good, since he cannot feel emotions at all, finding such things alien. Doma is seemingly incapable of caring about other beings or sympathizing with them for any reason. Even Gyutaro and Daki cared for one another, but Doma wouldn't even go that far.
Doma was also the one who killed Kanae Kocho, Shinobu's older sister, and it's a tragic loss that such a kind demon slayer was dispatched. Doma also makes a point of feeding on women, believing they are the most nutritious prey since their sex is the one that nurtures babies. Only a twisted demon would think along such lines and act accordingly.
3 Gyokko Fused Villagers Into a Grotesque Mass
Gyokko, the Upper Moon 5, liked to create and sell artistic vases, a business venture that Muzan approved of. He also took part in the assault on the swordsmith village alongside Hantengu, with Gyokko clearly being the eviler of the two Upper Moons.
Gyokko used more than porcelain to make his much-beloved art. To everyone's horror, he fused together a variety of villagers into a fleshy mass and admired what he had created, and there's little doubt that Gyokko has done such a thing before or would do so again, given the chance. Fortunately, the himbo Hashira Muichiro Tokito finished him off.
2 Enmu Manipulated Sick Children Into Obeying Him
At one point, Muzan killed off most of the Lower Moons out of sheer frustration, but he spared the Lower Moon 1, Enmu. Once Enmu consumed Muzan's blood to power up, he set out on his newest mission, attacking Kyojuro and Tanjiro's squad one night aboard the Mugen Train. In some ways, in fact, Enmu was the Mugen Train itself.
Enmu didn't even fight his foes directly at first. He put them to sleep with his special abilities, then sent a squad of children to finish off Tanjiro and the others while they slept. Enmu, as a true villain, had coerced some sick children into being his personal assassins, something not even the Upper Moons have been seen doing.
1 Muzan Kibutsuji Became the Scourge of Humanity For Selfish Reasons
The demon king himself, Muzan Kibutsuji, has clearly established himself as the anime's evilest character. Centuries ago, Muzan became the world's first demon, and he has since been fixated on finding a cure. Unfortunately, Muzan's chosen methods came at a steep blood price, with Muzan regularly making demons who attacked and killed people. Muzan didn't care how many people suffered, so long as he got the cure he wanted.
No matter his disguise as a loving family man in Tokyo, Muzan is a cruel, selfish, and exploitative creature with no particular redeeming qualities. He even casually turned a passing man into a demon, who attacked his wife, just so Muzan could create a diversion to get away from Tanjiro. He will also whimsically kill off his minions if they don't meet his lofty expectations.
