Vista is a second commander isn't he?
Talking about Yonko second Commanders, not only is Akainu's equal a Yonko's 2nd Commander
And till this date an Admiral has been unable to beat a Yonko first commander in a fair fight, something Mihawk's student did it in nearly dead state under 2 minutes time limit
Its better if you keep Mihawk's name out of your mouth, he is far beyond an Admriral's reach.
Right now you should be giving me a real argument on why Akainu can beat even Zoro.