Mihawk is the only shichibukai with no revealed (frozen) bounty and is reserved for the last so it proves my point if anything in that the best are usually reserved for the last. There obviously can have exceptions here and there, but it generally goes that route from simple power-scaling as well as the suspence in the manga in itself(you don't expect the final villain of the manga to be weaker than Arlong right?)
This is not at all what you said. You said Katakuri was INTRODUCED last, therefore he's the strongest. You did not say anything about being RESERVED for last, your argument relied on the concept of INTRODUCTION.
1. Portrayal places Katakuri higher than Cracker(higher bounty, last to be revealed, portrayed as the highest threat in the party according to Capone)
Don't backpedal now.
Either way, your argument fails, since there is no indication that Katakuri is being reserved for last. With Mihawk, we knew because he defeated Zoro and immediately proclaimed for him to come meet him once he's stronger, and the fact that Mihawk is the key part of achieving Zoro's dream. None of that applies to Katakuri. In fact, Oda has explicitly written it for them to avoid fighting PERIOD, so there's not even a plan for them to be fighting Katakuri at all(Though it might happen if the plan fails."
The Vinsmokes introduced so far have been portrayed to be scrubs. Yonji getting his face recked by Sanji.
That's Yonji. Saying the Vinsmokes are a whole because of Yonji's portrayal is like saying the Strawhats are scrubs because Usopp was beaten up by Trebol and Sugar.
Niji's face cracked by Sanji and only gaining edge due to threat.
Niji took no visible damage from that blow. His jaw was seemingly knocked out of place, which was immediately nullified by him setting it back with no consequences. There was no damage to him.
Not only that, but acting like one blow from Sanji dislocating Niji's jaw means he's trash is a pretty flawed argument. Chopper was able to knock a Pacifista backwards and draw blood from its mouth, which is more damage than Sanji did to Niji. And yet that Pacista was still as strong as the ENTIRE group of Strawhats.
Basing it one blow is very, very flawed, otherwise someone could link that panel of Chopper hitting the Pacifista and saying that he was clearly stronger because of it.
The best one is actually Judge and even him didn't seem stronger than Sanji considering Sanji was portrayed to be fighting him while lost in his own thoughts and him having to protect himself with scrubs, and Sanji himself is fodder to yonko commanders with his current feats.
Not every yonko commander is Cracker level. Snack wasn't. Doflamingo isn't and even if it is the case at the moment, by the time of wano arc, Luffy will be stronger, so there is nothing stopping current Zoro in accomplishing a feat Luffy couldn't
*inhales deeply*
Gotta love the smell of contradiction in the morning.