Any other answer than Chopper would seem weird to me. I hate how he's the doctor of the crew, but other characters continuously steal the shine in that regard (Law in Punk Hazard, Caesar in Zou, now with Zoro the Minks in Wano). He might have been involved, and the Ice Oni stuff actually was his big moment, but the other examples couldn't have been resolved without help. Although Marco was necessary with that virus as well, so...