So after chapter 218, I decided to see how big Oga's power had gotten in terms of scale. I was really impressed with how big his light-beam emblem had gotten compared to the coastline.
No surprise, Tamura drew a real existing coastline as a marker for scale:
So right now, Oga's emblem is large enough to engulf a city almost entirely. I'm starting to see how easy it could be for Beel to destroy the whole world if he wanted to.
Another interesting tidbit, is that this reveals a little bit more on where the characters live. Hiratsuka is a mid-sized city that merges into the outskirts of Tokyo. It kind of explains why we don't see any really congested areas in the background.