As far as the colloseum goes, luffy never took that much damage to be fair. Even against chinjao luffy kinda lucked out as chinjao had the whole head thing going on. Even if it had some effect on his stamina at the time he had plenty of time to recover as well. Overall the manga has shown luffy as someone who recovers relatively fast from fights. He did take some damage from bellamy though. Still, I would argue doflamingo did take significantly more damage than luffy ever did through all of that.
It's not about damage, but stamina mostly in the colliseum and beating all those DD henchmen after that. Luffy didn't get a lot of time to recover since right after his fight, he left the colliseum to go after DD in the palace. Against Bellamy he tanked his attacks and took some damage, obviously not on the same level as Gamma Knife but then again when you look at DD fighting after that, he didn't seem bothered by the Gamma Knife at all. There's no doubt it had some effect, as Luffy himself mentioned but I don't think it had that much of an effect thanks to his DF
I really don't see how luffy before gear 4 was in any form equal to doflamingo. At least as far as I can tell doflamingo consistently showed he was immensely superior. At best it was a matter of time until doflamingo would have won in more or less the same way he had won against law. Luffy could avoid doflamingo's attacks however doflamingo was by all intents and purposes not affected by gear 2 or 3. In turn doflamingo's attacks did hurt luffy. Gear 4 was a game changer in that regard but the manga conclusively proves it was not enough to actually beat doflamingo. Luffy simply didn't last enough to finish the job on his own. I don't recall doflamingo ever stalling for time either. He fights at a range because that is his thing to a great extent however he never made a point of running away or getting some distance between them. Sure, the issue luffy had was that he didn't last the extra second he needed to deliver the punch he needed... However that was not doflamingo's doing, that was luffy who punched doflamingo that far away. And even then, when luffy did deliver the last punch it was the absolute last punch luffy could use, after the 10 minute recovery luffy could do a single punch before passing out.
I don't agree with you here, Luffy was holding his own against DD and were roughly equal, I'd still give the edge to DD but the fight was even when he was using Gear 2. Obviously he lacked the strength, since he needed to finish the fight asap because of the birdcage. Gear 3 was too slow for DD, but with Gear 2 he was definitely holding his own, and both were hitting each other.
Of course Doflamingo's attacks will hurt more since they were cutting techniques, and Luffy is weak towards that kind of attacks.
The manga doesn't prove it wasn't enough, it only proved Luffy did not have enough time, imagine if he followed it up with a punch right after the Leo Bazooka and not just looking around to see if the Birdcage is still up or not, then the fight would've been over right there. Imagine if Luffy with his stamina at 100%, we can safely assume Gear 4 would last a bit longer
To be honest, I don't think the punch that did doflamingo in would have worked had doflamingo fought luffy at full strength from the start. Doflamingo only stitched himself up but his organs weren't healed, they were basically slashed cleanly in half. Even doflamingo makes the point that he needed more time to fully recover. Stitching is in no form or context healing, doflamingo was not well. Sure, he wasn't panting and that sort of thing but the whole thing should be seen as a testament to doflamingo's gargantuan strength, at least relative to luffy's. Had doflamingo not sustained the damage he had taken, it is very well possible that even luffy's second run with gear 4 would not have done the job. If luffy was able to use his gear 4 as he is able to use his other gears then luffy would definitely be able to take doflamingo on his own however that is far from the case. As it stands luffy needs 2 runs on gear 4 and have his allies chip away at every bit of strength they can from doflamingo along with actual armies protecting him while he recovers to win. In a scenario where the two fight alone at the peak of their strength luffy would at best use gear 4, pound doflamingo a bit and then run out of juice while doflamingo has a solid ten minutes to do absolutely anything he wants to luffy's immobile body. Luffy didn't win against doflamingo on his own, luffy beat doflamingo specifically because of every ally he had backing him up. Luffy won because he has the most dangerous ability in the ocean, to make friends of everyone he met.
Again, the Gamma Knife did damage DD, nobody is denying that at all... However, I think people are blowing the damage out of proportions... DD was basically fighting and keeping up the same performance after tanking Gamma Knife, his speed didn't decrease nor his strength overall. Surely DD has amazing stamina, much more than even Luffy is you ask me, but the Gamma Knife wasn't that effective to the point where it gave Luffy that much of an advantage
It also happened that the awakening technique was fairly convenient to keep Luffy away since he's close range, can't say DD was the best matchup for Luffy overall
