At the risk of glazing I'd say it was Kizaru's EH performance as a whole.
Powerwise he showed very good CQC and durability. He stalemated, outlasted and fed an immensely powerful enemy while trying to accomplish the difficult mission of killing his best friend. By the end he was never fairly defeated and didn't even receive a tear on his suit.
He finished the arc with excellent character development for both himself and Akainu, and even gave us some top tier memes in the process (Maintaining the agenda, Damn that's peak, Pizzaru, shocked face, Doordash/take my lunch Nika etc).
Akainu's bounty is a really big deal ofc, but at least for me, Wizaru's feats are what really make said bounty have more weight.
(Plus Kizaru feeding Luffy got waaay more wailing and gnashing of teeth from the Reddit powerscaling crowd than Sakazuki's bounty did, at least in my experience)
As for the rest, Kuzan's performance was good but not phenomenal. The boxing thing was cool and his relationship with Garp felt better written than Kizaru's with VP.
GB and Fuji's sword unlocks are intriguing and promising, but don't mean much to me until they get more feats.