>>713229715Square Enix explains it in a side material that the reason he is immortal is because his soul isn't actually in his body but somewhere else, so every time he is injured or die he would regenerate unless you find where his soul actually is and destroy it. It is just a lame lich situation that is exaggerated because he is the only one with that in verse, so I'm pretty sure Kefka can do it by just nuking continents randomly eventually