A Brief Explanation

It depended. People kept worrying I'd make the power scale collapse, so here was a rough explanation.

A level 100 combatant from Nazarick, at full strength, had their greatest destructive power against the surface described uniformly as city-level [small city or town level]. World Items, meanwhile, had all kinds of effects due to their settings and couldn't be judged by power alone; they were the power of rules. [Like water extinguishing fire, or the law of conservation of energy.]

So the people of Nazarick were strong, but purely in terms of power, they were not without opponents.