I dont think either Bellamy or Saint Charlos are helping your case here...
Both are scrubs, that's why they were defeated by a single punch.
Nobody worth his salt would ever be taken out by Luffy's one punch.
Weapon is by definition superior otherwise what is the reason they are invented...
Because he wouldnt be able to take out people weaker than Katakuri who are used to getting hit unlike Katakuri who isnt.
It is Katakuri's weakness that he brought onto himself by avoiding the hits. The main difference actually is that one handles blunt damage well while the other doesnt.
Luffy wasnt strong enough to beat Doffy on his own. We both know that.
Doffy takes hits far better than Katakuri. If Katakuri had near immunity to blunt damage he would tank hundred of Luffy's punches too.
Luffy's punches are simply weak. Even Garp's punches are weak and they are far above Luffy's...