Akainu killing Ace is not impressive at all

This is by far the most overrated Akainu's feat. The only reason it's still being brought up it's because Akainu has gotten basically nothing over the last 15 years, so every little thing he did gets wanked to high heavens.

I'm going to split this quick analysis into two parts: in-universe and out-of-universe.

• In-Universe

Even wanking Ace to YC1 with his novel doesn't make this feat good.

We have prime enraged Akainu who has a devil fruit advantage over Ace being able to kill him after he threw himself in front of his attack. And Ace wasn't even in his best form because of the tortures he had to endure while he stayed in Impel Down (not that it would've changed anything).

So I don't think it's controversial to say that Akainu killing Ace isn't a good feat in-universe.

• Out-of-Universe

This is where the most wanking comes from. Since death is almost non existent for named characters in One Piece, Akainu killing Ace is seen as this incredible feat because it's one of the only times Oda let a character kill another.

And since Oda doesn't like killing characters, the fact that he made an exception for Akainu seems incredible, something to consider when it comes to his narrative and future fights.

All while not knowing that Oda's reason to create Ace was to kill him. Ace was just a tool for Oda to make Luffy stronger. His popularity gave him a few more years but in the end that's what he was written for.

It's not "Oda wanted to make Akainu look good" or anything like that, it's "Ace needed to die". And that's also why his death came so suddenly after a yo daddy joke.

Overall this feat it's absolutely nothing no matter how you read it