Concrete_Regeneration - I would just be prolonging my suffering >.>
Random Power:
How I would beat: Plural so I will go with multiple entities. At least three.
The first entity is named "Physical Baptiste", (all their powers are randomized in the Personal Physical category)
This entity cannot be seen without Advanced Observation Haki. They appear to be precisely 509 cm, the same height as Katakuri. Once emerged, they do have a physical body and can have the blows land on them.
"Physical Baptiste" can use Strength Calling to the uttermost potential, allowing them to reach absolute levels once they call for strength essentially. They call strength in attempts to fight Luffy with their own version of Armament Haki, to punch them beyond the layer of their rubbery defense and even with their Advanced protection too.
"Physical Baptiste" favorite type of power to use would be an absolute variation of Lung Capacity. Allowing them to indefinitely inhale all the oxygen from any of Luffy's moves that could contain the fire. Therefore extinguishing it before it could be released. They could even cause a hurricane just by simply exhaling the oxygen at stupid speeds. Even mimicking their Gear 2nd form as they attempt to inhale all sorts of oxygen to master their blood pressure.
If Luffy were to use their G5 technique, "Physical Baptiste" would begin to get stronger as long as Luffy feels the drums of liberation course through them. Which was described to be a positive feeling. Even in general Luffy's happy attitude, "Physical Baptiste" would get far stronger than theirs in every category!
I'll edit the next two entities when wanted: I decided I would already win just by "Physical Baptiste" forming. My JoBro has arrived to destroy Luffy beyond difficulty.
I was about to make a joke about him not being able to swim, and just needing to get him to the water… but then I got this of all possible things.