@comrade
Anyone who has eaten a Logia-type fruit can become an element like fire, ice, lightning, etc. In this state, they can act independently of the limits of their corporeal bodies. Most physical attacks are ineffective against individuals in this form, which means you must fight them using the element's weakness or with Haki.
We have seen cases in which the weakness of the element resulted in victory, as was the case with Luffy versus Crocodile and Akainu versus Ace (its magma consumed its flames, thus amplifying Akainu's attacks), the case of Aokiji and Akainu would not be a case in which the Does Akainu have the advantage in the match? I mean, in order for Aokiji to properly injure Akainu he simply had to use Haki thus wearing him down with use, but is it essential for Akainu to use Haki to injure Aokiji?