The Demon King has possessed 10,000 civilians, turning them into a zombie army marching on the capital. A "Good" harem lacks the firepower to kill 10,000 without exhausting themselves. A rival "Evil" harem has a spell that will kill all 10,000 civilians instantly—but the spell requires the sacrifice of one of the harem members (the healer, who is unwilling).
Here is a comparative review of whether or Evil (The Anti-Hero/Villain) handles the apocalypse better. harem fantasy good or evil will save the world better