User blog comment:Gametroller Prime/Four Great Powers?/@comment-25501246-20160218230245

The Worst Generation are not a power because they're not an allied organization. They're rivals between themselves.

The formula is that the Marines + Shichibukai more or less = 1 Emperor. Because Emperors are not allied with each other, but have several subordinates that can match Shichibukai and Admirals, as shown during the Marineford War. Marco and Jozu could match Admirals, Vista could match Mihawk, Curiel and Jinbe both could match Moriah, etc...