The only two people that have harmed Akainu are Whitebeard and Ao Kiji. Two people who you could say are good matches against Akainu.
One has to have ridiculous buso haki capabilities or the ability to attack without using ones body in order to hurt Akainu without burning themselves.
People like Luffy, Garp, Sengoku, Chinjao, Zephyr etc primarily attack with their fists/feet/head and so would need ridiculous levels of buso haki in order to negate his magma. Even Whitebeard hasn't shown such feats and was only able to strike Akainu through long range Gura punches which didn't allow Akainu's magma to touch his skin.
Ao Kiji is also a good match up against Akainu because he can use his long range DF attacks (ice) against Akainu's magma. Other Logia's such as Kizaru and Enel wouldn't be able to attack Akainu with their DF and would have to resort to haki coated body parts which unless they have unreal buso haki would get burnt. This is because one cannot coat long range DF attacks such as Kizaru's lasers or Enel's lightning with haki.
Akainu has even been shown to negate the haki effects of strong adversaries such as Marco and Vista. Imo Akainu was strong enough to beat the old Whitebeard at Marineford. He got back up like nothing happened after Whitebeard unleashed his fury and if the fight had continued, it's likely he would have won.
Imo pre-skip Akainu can only be beaten by Shanks and Kaido and maybe post-skip BB. If he has been training over the 2 years (having witnessed the threat of Luffy) then expect him to be on par with the likes of Shanks and Kaido.
One has to have ridiculous buso haki capabilities or the ability to attack without using ones body in order to hurt Akainu without burning themselves.
People like Luffy, Garp, Sengoku, Chinjao, Zephyr etc primarily attack with their fists/feet/head and so would need ridiculous levels of buso haki in order to negate his magma. Even Whitebeard hasn't shown such feats and was only able to strike Akainu through long range Gura punches which didn't allow Akainu's magma to touch his skin.
Ao Kiji is also a good match up against Akainu because he can use his long range DF attacks (ice) against Akainu's magma. Other Logia's such as Kizaru and Enel wouldn't be able to attack Akainu with their DF and would have to resort to haki coated body parts which unless they have unreal buso haki would get burnt. This is because one cannot coat long range DF attacks such as Kizaru's lasers or Enel's lightning with haki.
Akainu has even been shown to negate the haki effects of strong adversaries such as Marco and Vista. Imo Akainu was strong enough to beat the old Whitebeard at Marineford. He got back up like nothing happened after Whitebeard unleashed his fury and if the fight had continued, it's likely he would have won.
Imo pre-skip Akainu can only be beaten by Shanks and Kaido and maybe post-skip BB. If he has been training over the 2 years (having witnessed the threat of Luffy) then expect him to be on par with the likes of Shanks and Kaido.