First of all Luffy used gear 4th against a fucking ship
Yeah because it was a proud battle between him,Law and Kid, he wasn't force to use G4 as Ulti did, yet you didn't want to listen to this point.
Also Luffy said and hype Ulti power, he see probably via FS that Ulti was almost releasing a insane attack, in the fact that he need G4 shows you the power of Ulti.
Second, there's no indication that Luffy used haki, and the sparks were on Ulti's head before Luffy's head made contact with her.
In the panel we literally can see CoA, his head was covered in black armor. And she die it in her Base form.
Third, Luffy has been oneshoted by Big Mom and he woke up after few minutes, Luffy has been oneshoted by Kaido and in Udon he was already awake.
Against Big mom he said that his energy was taking out, it wasn't a physical attack.
Against Kaido Luffy was down for almost one day, you can't compare it to some seconds of Pageone and Ulti who seems beeing fine in some seconds after the clash.
As I said Luffy would still beat both, but why is it so hard to accept that Oda do anything to hype the flyers and giving them really good feats?
As I said one broke Luffy CoA, the another tank straight G3 uppercut attack(to remind, Doffy was on his knee by a far weaker attack(red hawk) and weaker Luffy), then Ulti push Luffy to G4.
Aren't these feats impressiv for the weakest flyers? We didn't even see Sasaki and Who's Who in action who are above Ulti!!!
Right now Oda really make a good job to perform really good villians, the flyers aren't jokes and the tension is very dangerous. Look at the flyers, can you imaginen Jack,Queen or fucking King in action?