A single evil entity by itself is powerless

A singular evil entity by itself is fairly powerless.
It has to tap into the evil in others to really work.
So evil exists everywhere.
The entity you cleanly identify as evil is only the top of the iceberg.
It appeals and brings out the unconscious and shadow of society and humanity itself, which is carried in everyone.
On the surface, only the perpetrator of evil is clearly visible.
But it cannot really work unless the entire system supports it.