Look at how strong Base Kaido is. Kaido hasn’t even used Haki yet, or his hybrid. And then there’s Awakening, which Kaido most likely has. How can Akainu possibly keep up with full power Awakened Kaido? His Raimei Hakke would be much faster and stronger than what has been shown, and his durability and regen would also be increased, so Akainu’s attacks would be less effective.