The canon power scale is as follows:
Kaido > Akainu, Kizaru, Fujitora, Green Bull, and the Holy Knights, as Kaido was the strongest person in the world.
Shanks > Green Bull, Kizaru, and Fujitora (in the Red movie), and Akainu due to the Marineford events.
Blackbeard > Aokiji (his subordinate) = Akainu (pre-timeskip), which means BB is superior to Kizaru, Green Bull, and Fujitora.
Big Mom is easily superior to Akainu due to the fact that she reached the same position as him based solely on her physical stats. Therefore, Big Mom > Akainu, Kizaru, Green Bull, and Fujitora.
Big Mom is also not losing to any of her subordinates, so Big Mom > Aokiji, who is equal to Akainu.
@Kawatsuki