Gassiev. Won every round against a unified champ that was supposed to be competitive. AJ 1 and Fury 2 were good runners up.
AJ 1 because he was moving up and fighting a bigger stronger champ who most people thought would beat him and put on an absolute masterclass winning almost every round
This is the obvious answer - Joshua didn't fight particularly badly, Usyk just showed how ridiculously good he is. Dare I say it, I'd put Bellew high on Usyks list too... Plenty on here love to hate the guy, but he's tough with good ring IQ. Usyk just went up and up through the gears and not only beat but completely mentally demolished Bellew - to the point that Bellew can do nothing but gush about how incredible Usyk is to fight, how he has an answer for everything, etc.
I think it's actually a toss up between AJ 2 & Fury I - that was the best Joshua has been, but Usyk still shut him out and his response in round 10 after AJ having a sniff of success was phenomenal. Similarly, Hury had Usyk looking as uncomfortable and out of sorts as he had ever been rounds 4,5&6, but Usyk made the adjustment in round 7 and went through the gears to almost stop Fury Gassiev was a shutout, but Usyk was a nightmare style matchup for Gassiev.
He had to overcome adversity and an equally skilled fighter against Fury he stuck to a risky but required gameplan of constant pressure and turned the tide after having some of the toughest rounds of his career. Therefore Fury 1 takes the biscuit. AJ is a bodybuilding bum that was just a big of fun for Usyk.
Joshua wasn’t ready for Usyk’s elite pace and smarts. He adjusted in Rounds 5-6, landing some good shots and looked like was coming back, but Usyk flipped the script late, outworked him with feints and angles, owned the initiative, and nearly finished him.