Enmu

Enmu was a demon who was born from the blood of Muzan Kibutsuji, the progenitor of all demons. He was a sadistic and manipulative demon who enjoyed toying with his victims before killing them. He had the ability to create illusions that were so realistic that they could even fool the Hashira, the strongest of the Demon Slayer Corps. Enmu's most notable feat was when he orchestrated the Mugen Train arc, in which he killed over 40 people and nearly killed Tanjiro Kamado and his friends. He was eventually defeated by Tanjiro and Nezuko Kamado, but not before he caused a great deal of damage. Enmu was a powerful and dangerous demon, but he was also arrogant and overconfident. This led to his downfall, as he underestimated the strength of Tanjiro and Nezuko. He is a reminder that even the strongest of demons can be defeated if they are not careful.