But talking in terms of individual people it would be Tanjiro Kamado; it was he who ended Muzan. At the same time, it's worth pointing out that Tanjiro, in fighting with Muzan, killed him in actual fact. Muzan's final defeat was brought about by this continuous striking and all-out group attack on the part of Tanjiro, Nezuko, and Kanao: Timing was just as important as coordinating their efforts. Just one point to remember, though: Tanjiro was using family secrets... Sun Breathing This style rather incongruously from an odd historical perspective given that both its creator and mode of combat are products unique to his household was passed down totally orally among the few members of his clan who survived long enough to do so. And only this school of demon-killing can, it seems, actually kill an organism as potent as Muzan.