As Sealas already stated,
Evil is always exit, and
in order to erase this "Evil" he need to destroy all of existence and rebuild a new one. And no, in the scan, he didn't mention evil beings or anything similar, he literally said
Evil itself
Beside, as others had said it already, if Sealas only want to destroy all evil beings, he already has power to do so, he literally has destructive power to destroy the entire multiverse,
warp reality and create new world, if he just want to end all evil beings simply, he could just blow up all thing, then make new world without a single evil beings. or if he doesn't want to destroy reality, his powers allow him to delete every single evil beings with his stats alone. But he keep slamming the fact that in order to actually eradicate
Evil itself, (not simply evil beings) he need to destroy everything, rebuild reality from the ground up and reforge existence, despite all the power he has. This mean:
1. Even when he could destroy the current reality and make a new one, evil beings keep appearing
2. He directly stated in order to eradicate
Evil itself, everything need to be destroyed, he will rebuild reality from the ground up and reforge existence
combine two points, we could see that
Evil itself is literal fundamental abstract aspect of reality that responsible for evil beings, and Sealas need to eradicate it to actually stop evil beings coming out. Which literally fall under qualification for concepts,
Quote from CM page, now come to our case, the suppose concept is Evil, "evil" participating in this Evil concepts and this Evil concept shape all evil beings as they are under evil concept's area of influence
Thus Evil is qualify for Concept
Evil Thoughts, Ideas is support arguments for this Evil being abstract, not some concrete thing or some living being. Janemba is stated to be incarnation or manifestation of Evil Ideas is another supporting evidence for "Evil concept shape all evil beings as they are under evil concept's area of influence". Evil Ideas energy can warp physical reality and distort laws that governing over reality also another supporting evidence to support that this Evil can affect physical reality and metaphysical aspects that governs over said reality (
law is considered metaphysical aspect)
he didn't overwriting suppose concepts, but rather merge with them, become so concept directly, that why almost every pieces of media stated he becoming
justice and order itself, and again is stated that
he can control the universe, that mean these suppose justice and order can actually influence and govern, control physical reality. And IZ, being justice and order itself, directly, or we could say he merge with those concepts, becoming sentient abstract concepts
And before anyone again asking what he can do, that is literally just asking on plot holes thing
Alright, back to rest, my work load get heavier these days