The difference is one is leading them because its their job and the others follow the other through other means or reasons.
Dont get me wrong Akainu is him but Rocks seems to be HIM.
Nah, the thing is, Oda views beating/killing an admiral an extremely valuable thing in the One Piece world. He granted this feat only two characters for now: Akainu and Xebec.
People were trying to discredit Akainu by stating "But that's just his job leading the admirals" without including the
Why behind it. Akainu had to beat
another Fleet Admiral candidate - someone who was skilled enough to be entrusted this position by SENGOKU HIMSELF - to get this position. That's not just "killing
an Admiral", that's "Beating Kuzan." Even Blackbeard wanted no smoke from Kuzan and it's confirmed that BB is Xebec's son.
It's also not like they just follow Akainu's orders out of obligation (as Admirals are, they mostly do not even do that lol) but you have a freaking monster like Aramaki viewing Akainu like a role model.
Whether Xebec was a rookie or not, what matters is that he
became famous after killing an admiral. That's obviously an achievement only a very very small handful of fighters can do in the One Piece world.