Him being called a “Fallen Angel” refers more to his character than to a specific event.
Him and Angel are at opposite ends of the morality spectrum. Angel, who’s technique has a move called “Jacob’s Ladder” which is a biblical connector between the divine and earthly realms, refuses to incarnate into her host, as that would permanently kill or overwrite Hana’s being. Technique Extinguishment also permanently destroys techniques, barriers, Cursed Objects and Cursed Spirits. It is also implied to work against people with “evil intentions” tho that could have just been a joke/hyperbole.
Sukuna’s technique is also presented with the same divinity as Technique Extinguishment. It embodies both a refined culinary art and also a divine mode of worship. Hence we get the two translations of his Domain being “Kitchen” and “Shrine”. The culinary part of his technique is more about how he uses his technique and how he interprets it. He prepares his victims with Cleaver and Dismantle and cooks them using Divine Flame. The Shrine refers to how Sukuna acts like acts like a deity, he tells Jogo, Mimiko and Nanako to bow their heads in reverance. He was worshipped in the Heian era, and his body even mummified. He is an inversion of the Sokushinbutsu ideal, he “transcends” through his indulgence of his own desires.
Angel calling Sukuna “Fallen Angel” is a character description. Its a biblical ascribing of Sukuna’s condition (Angel is an Arabic sorcerer). And the more interesting interpretation isnt Luciferian, its referring to the Watchers. These were the “sons of God” who descended from Heaven to teach humanity forbidden knowledge.
Angel is ascribing Sukuna title derived from beings who violated God’s law and crossed the boundry between divinity and humanity.
Sukuna both plays into and subverts this biblical title.
Another interesting thing is how Sukuna climbs Jacob’s Ladder. Which outside of the practical context of HOW he did it, symbolically its showing us the “Fallen One” ascending back up to heaven via profane means (Curses). Which while being completely different religious symbolism, links back to how Sukuna achieved Sokushinbutsu mummification and embodies the “false Buddha” archetype within the story.
Sukuna is a character who’s divinity and profanity you cant seperate because he’s so intertwined with both symbolically.
this nigga never went into more detail about this btw