Usyk without a doubt, Lewis is a fighter who was knocked out by Rahman and McCall and has a questionable win over Mercer, I doubt Lewis would beat Usyk.
Tough one. Besides the Klitschkos, I thought Lennox could probably beat all of the other ATG HWs because he had the size, skills and power. With Usyk, Lennox isn't that much bigger, but I think Usyk probably has a speed advantage. That speed advantage probably leads to Lennox getting drilled by a counter. Maybe Lennox survives it, but I think the fight kind of resembles the AJ fights where he is getting tagged and losing those rounds.
You named 3 heavyweight contenders/ex champs Lewis had issues with and avenged. this is pretty much the size of usyks win resume at hw. it’s like when ppl say “I’ve forgotten more than you know”
Lennox is too big, and he has beaten too many good HW fighters, I think. Fighting Euro-level Dubois (x2), a post-Ruiz AJ (x2), and a post-Ngannou Fury (x2) is not on the same level as beating Holyfield x2 (robbed in the first one), avenging both his losses, beating David Tua, or even the 1-round Golota blowout, which is a heavily underrated win. Usyk is probably on par P4P, because he was a CW moving up, but the idea that he is invincible has taken on a mythical form over the last couple of years. Chisora had his success against him, and Fury had him in trouble with an uppercut; Lennox arguably had the best uppercut in the history of the division, and I think he'd have had Usyk in trouble. Usyk would have his success, obviously, it'd be a great fight, but I think Lennox gets the win here. He's got the power to discourage Usyk over 12 rounds.
For me the likes of Lennox Lewis, Riddick Bowe, Evander Holyfield, Mike Tyson were easily class above the likes of Fury, AJ, etc.