Egghead has utterly destroyed everyone's powerscale, this is insane.
The only way any character alive in One Piece is low/neg-diffing G4 Luffy is if Luffy doesn't use ACoC.
Luffy is a sky-splitter. He stands alongside old Whitebeard, Big Mom, Shanks and Kaido. Don't let Egghead's foolishness distract you.
Luffy did not use ACoC vs Kizaru until White Star Gun. Luffy is not a top-tier unless he is using G5 or ACoC. ACoC-less G4 Luffy is high YC1, around the same level as King - that is the version of G4 Luffy that Kizaru beat. We already know that without ACoC, Luffy is below Yamato who isn't even top-tier herself, she's an inbetweener.
ACoC is defined as the power of the strongest. It is an unbelievable power-up that simultaneously takes one's offense and defense to ridiculous levels. Luffy has it to a sky-splitter's degree - if he is not using ACoC outside of G5, he is not a top-tier; it is that simple. Kizaru basically fought post-Udon Luffy and people went crazy.
No character alive bar Imu/Gorosei is beating G4 ACoC Luffy any less than mid/high-diff, and the only ones who could go as easy as mid-diff are high top-tiers themselves, which Kizaru isn't.
And if Luffy decides to use ACoC against Scopper, then Gaban doesn't make it past chapter 1140.