I've never really… spoken to you on the forums, but I've always thought of you as the supposed "Arlong Arc Master". That's why this post surprised me.
<<< "Resident Gyojunkie". That means biased. Badly biased. I'm fairly convinced Arlong could beat Ener by shorting him out and Lucci by smelling like delicious tuna and leading the giant kitty off a cliff into the sea.
Last I checked, Luffy smashed Arlong so hard with Ono, that he was shot down 3 stories of Arlong Park and then the whole building collapsed. In my opinion, it wasn't the 3 stories he broke through that killed him. It was the force that blasted him 3 stories that killed him. If Luffy hit him with that kind of power again, he still would've died. Looked to me like he was dead before he even made it to the 2nd floor.
Referencing Chapter 93, Page 17.
The top panel shows that a table broke Arlong's fall.
The centre panel shows the hole punched through Arlong Park.
We can see:
-(unclear, possibly larger tiles)
-(unclear, may be a carpeted floor)
was pushed through.
None of these (which can be identified) are very resilient materials. They don't take much force to push through (compared to metal plates or thick concrete, for example). If they were, those martial-artists who can break through several boards with a kick would be more impressive.
Furthermore, each of the layers of material he was pushed through would swallow some of his momentum. Indeed, it doesn't look like he made much of a dent (left middle panel) in the ground floor.
We see (left middle panel) Arlong's teeth broken, his nose bent, and bleeding from the mouth. None of these are major injuries– we've already seen his nose can be bent back and his teeth are expendable.
I don't see this as a fatal blow. It's impressive, but not fatal. I see Arlong as down, but not out, at that point. He was entombed (buried alive or crushed to death) when Arlong Park collapsed atop him.
I think the only reason Arlong Park was destroyed was so people would question Luffy's death, and/or it was some metephor shit that stated Arlong has figurativly "fallen".
I saw it as a combination of the structural damage from having a 200kg gyojin shoved through the building, another 200kg one kicked through it, and a huge amount of kiribashi damage to structurally important walls.