What's the point with that quite lackluster story in Endwalker?

[CrownySuccubus]

My favorite character in all of fiction is a brutal mass-murderer who enacted an elaborate plan to slaughter their entire family.

Which character is this, by the by?

Incidentally, my favorite all-time villain (although Emet-Selch vies for the spot) is Kuja from FFIX -- who was a genocidal, racist narcissist who had such little empathy for the deaths of other people that he ordered his minions to painfully murder a child, tried to kill innocent people for no reason other than the fact that he found it funny, and then decided to obliterate all existence everywhere because he thought it was unfair for anything to exist after he died.

But Kuja was such an over-theatrical, card-carrying jerk that I couldn't help but feel entertained. Hell, I even thought his reasons (though still unsound and cruel) were at least valid; Kuja was fated to be born and die as a slave whose life didn't matter, so he jumped to the extreme opposite end and decided that ONLY he himself mattered.

Unlike Hermes, Kuja actually DID figure out why he was "wrong" just before he died, and though that in no way justifies or undoes his horrific actions, it was still interesting development and his selfish actions had the unintentional effect of teaching the rest of his race how to think for themselves.