You are somewhat correct. We cannot argue that August noted Ajeel
might have died.
Let's analyze the situation:
First of all, Laxu's casual nuke is smaller in AoE than many of you think. It seems about as large as Dimaria turning into Chronos... (Although, on the other hand, there is a calculation which puts that nuke about large mountain level, so I won't be the one to judge its size. Calculation source:
http://vsbattles.wikia.com/wiki/Thread:71118)
Secondly, August doesn't say that the attack
would have killed him, he just says "Losing one's comrade is a terrible thing, Azir". It is a suggestion of something that might have happened. And trust me on this, I'm a linguist. Of course I don't know if that's the most accurate translation since I don't know what it says in Japanese (nor do I know Japanese) but if it is an accurate translation, it is not saying he
would have but rather he
might have died.
Thirdly, in order to squash August supposition (not statement), Ajeel denies it with emphasis: "You're not suggesting I might have died from that attack..." <- incredulity, disbelief. Ajeel cannot comprehend how it might have shot through August's head that he might've died from that attack. Then he says "Be careful you don't go senile in your old age, August". Irony with hues of threat. He's mad at the sole fact he might've envisioned him dying from 'such a pitiful attack'. He's also questioning his reasoning and judgement. So I trust more Ajeel, who knows his durability better than a third party who's just been questioned of being senile for not encompassing Ajeel's durability.
Then if we go by feats, Ajeel is a combination of very proficient CQC (high speed, brute strength), vast amounts of MP (seemingly superior to Laxus') and a bit of hax-ish magic (he can make you dry by touching you = he can literally take life out of you, + he can assimilate into the sand + he's partially intangible + he can create sand monsters, sand colossi, etc.)
So, I can 'understand' someone would say Laxus is vastly superior to Wahl because he could oneshot him even if handicapped + Wahl being immune to Laxus' kind of magic, but saying he could've casually killed Ajeel is absurd. And I love Laxus, but come on. Laxus can't casually kill any spriggan. Neinhart maybe? Dunno.