Not impressive:
10 - Usopp: Nothing really impressive about his performance... Ulti and Page are leagues above Usopp so he couldn't really do anything impressive.
A little bit impressive:
9 - Brook: Some new nice ice abilities, and he defeat 1 Number and a few Gifters while they were distracted, that isn't that impressive.
8 - Jinbe: It's a impressive him being capable of throwing Big Mom around and defeating WW with mid/high diff but it isn't surprising... We know that Jinbe is a freaking monster so he need to do something like defeating a Yonko commander to really be impressive.
7 - Nami: She is in this place mostly because of not being knocked out by one Ulti headbutt, sending Ulti to the ground with her clima tact after getting enraged, and because of the insane new power up that is Zeus+Clima tact.
Impressive:
6 - Franky: Hitting a motorcycle into Big Mom face, challenged a Yonko with zero fear, and he defeated a Tobi Roppo... The only reason he isn't higher is because base Franky is already strong, then with the Shogun he becomes SUPER powerful, it's just that the fandom underrates him.
5 - Chopper: To analise and produce a cure for the Oni Virus on the spot and also creating a way to administer the cure to thousands of people at the same time it's pretty impressive... His Monster point time limit also improve a lot, and he even manage to flip over a giant Brachiosaurus.
4 - Sanji: His fight with Queen shows not only how powerful he was even without the Germa power up, but also the insane boost in his physical stats after that power up.
3 - Luffy: His growth rate is insane especially after the Conqueror's haki coating... Even Kaido is starting to recognising him was one of the big powerhouses in the world... Ofcourse the cloud splitting clash is the pinnacle of how impressive he has been in this war... He isn't higher because he is the main character so he already expect him to be very impressive
2 - Zoro: Taking the antidote from Apoo in a single seconds of rage with one attack... Unlocking Conqueror's haki... Cutting Kaido's scales and even leaving a scar... Stopping a combo attack from 2 Yonkos for a few seconds... Probably going to fully master Enma in his current fight with King... Despite being insane overrated in terms of power scaling by his fanboys, we can't deny that Zoro has been very impressive.
1 - Robin: It may sound strange to put her at number 1, considering the only thing she did was fight and defeat a Tobi Roppo, but the fact that Robin really hasn't got the chance to shine in a actual fight without just being suport, makes me and the entire fandom underestimate her because we never see her full capabilities as a fighter... So her creating a giant clone of herself, using fishman karate and pulling out that crazy demon form was so impressive... I thought she couldn't defeat Black Maria without Brook, because of her lack of action in the series... That is why Robin impressed me the most in Onigashima.