Akainu is standing next to no one as far as we know, from feats to portrayal and now even databooks blatantly say he was the strongest marine even during the Summit war.
As for Kizaru, most likely slightly stronger than Aokiji, but in terms of plot relevance with the current admirals Fujitora has him beat, then we have Ryokugyu with some solid feats.
Kizaru isnt really that special lol