If we're talking about attack power, than I would say WB-Roger clash, the most unbelievable clash ever actually shown.
If we're talking about will and determination, then all impel down-Marineford actions of our future Pirate King, Monkey D Luffy, step up as the best feats. 2% probability of healing from Magellan's venom, in some days and he recovered in just some hours.
Mention of honor for Zoro's "nothing happened", Oden holding for almost 24 hours when WB left WA and his legendary 1h boiling torture.