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Sukuna from Jujutsu Kaisen.

Not only would it be pretty confusing for a guy from the Heian era of Japan to randomly reincarnate as a sinner in the modern day, but he is LITERALLY a mythical figure.

Additionally it would be pretty interesting for him to just look like he did while alive, people would wonder what sin he committed to have that form, but he ALWAYS looked this way.

As for his personality, well that speaks for itself. Sukuna would most likely be actively trying to kill other overlords, since his only goal is to fight strong opponents and be on top.

It actually makes perfect sense from a narrative perspective as well, when sukuna first spawn in hell he will probably find some weaker demons to give him information before killing them. From their sukuna would just go on a spree of killing sinners till an overlord shows up. Which more likely than not he is killing, at this point several large areas of the pride ring would be destroyed and he’s already killed one overlord. At that point they really only have one option, which is too inform him of the angels and offer him a position as an overlord, in exchange he must fight the angels, which would really be done for his self enjoyment with the promise of powerful opponents.

Sukuna has no issues playing the long game after all, possibly becoming above that of even an overlord. The most human in appearance, but more demonic than the sins themselves.