i think a lot of kefka's charisma comes from the juxtaposition of him being this goofy manchild henchman who will then immediately switch to being extremely dangerous without any change in personality
like. you have villains that are scary that will also have funny moments, or bumbling bad guys who have a moment where they show they're serious, but rarely do you get both at roughly equal intensity.
I think Quinn put it like... Kefka is your average Saturday morning cartoon villain going, "I'll get you next time, you meddling kids!" and then next time he does a fucking warcrime.
tako tako♪tako tako♪