I was thinking about how strong enemies show up in manga. After them, an even stronger enemy shows up, and after them, an even stronger one... so what happens at the very end? It's like thinking about the edges of the universe. Once you look at the world around you, you realize that being a "strong" person means not doing bad things. An enemy who does bad things is a person who has a spiritual weakness, and what's truly scary is when someone takes that weakness and uses it to lash out at others.