All of the Admirals are likely 1 step below the Four Emperors. I think it would be realistic to say that if Akainu was a pirate, he´d probably be around the 500-700 million range.
Aokiji is the least hostile and probably the weakest too, though it´s hard to say how they compare against each other.
Akainu is the most hostile and potentially the strongest of them. Lava is one of the most ridiculous powers imaginable, being both heavy enough to choke out fire and gas/air and still liquid, oh and it´s atleastat least 1000 degrees Celsius as well.
What iI want to say though is that iI think Kizaru is the strongest of the Admirals. Think about this for a moment. You can counter ice with fire and other heat-related things or things that cantcan´t be frozen. How the hell do you counter light? Light moves at 300 thousand kilometers a second (and therefortherefore hits with that force too, making Kizaru potentially the physically strongest character in the One Piece world), is intangible, can bounce off of things, can cut and pierce things in the form of a laser. That´s probably the most overpowered possibly Devil Fruit power.
To put it shortly, while they aren´t the most powerful characters in the series, the Straw Hats probably still don´t stand a chance against one and they are pretty close to the top.