Information is missing on who killed Sukuna. The contexts provided do not specify an entity that directly killed Sukuna. Instead, they describe Sukuna as an extremely powerful sorcerer who became a cursed object for a form of immortality [3]. He was thought to have been defeated by ancient sorcerers, but it's suggested that he may have actually orchestrated his own survival using Kenjaku [2]. At the end of the Shinjuku Showdown Arc, Sukuna is defeated by the protagonist Yuji Itadori, but not killed [citation:4, citation:5]. In a later arc, Yuta Okkotsu, another powerful sorcerer, battles and defeats Kenjaku, but Sukuna's fate is not tied to this battle [8].