I'd say Muhammad Ali due to his constant movement and feints, atg jab, counter right hand and atg hand speed, I think Ali could do better than Tony Bellew but then again Lewis actually had KO power unlike Ali, a stronger offense, went to the body and his uppercut would be very dangerous here. He was spamming that uppercut against Mavrovic
Ali. Lewis would get utterly bambozzled by Usyk’s footwork, unable to get going with his jab and he’d eat Usyk’s own jab and left cross all night long. Ali actually had the athleticism and mobility to dance with Usyk, which takes away one of Usyk’s key advantages against these lumbering SHWs. He had a demonic right hand that would come in really handy against a southpaw, and he was a very tricky and intelligent guy, far more than Lewis and what Usyk is typically used to. Would he beat Usyk? No but he makes it closer than Lewis would I reckon.
First you have to ask what problems they woudl both present. Ali would be faster, and that is not going to be good for him. Lewis would present the same problems as Joshua and Fury. The difference is that if Lewis couldn't outbox him, he woudl just turn it into an Irish brawl.
I think I would Ali give him more trouble. Usyk is highly skilled but not a big puncher. He and Ali are the two smartest heavyweights I’ve seen in my lifetime. I think that would negate the usual intelligence and boxing IQ advantage that Usyk has. Also, because he is not a big punchera lot of Usyk’s wins at heavyweight are based on cumulative effect and he would have a much harder time hitting the Ali of the 60s then he would have hitting Lennox Lewis at any point in Lewis’ career. All in all, I believe that Ali would be consideringly more difficult for Usyk than Lewis.
Lewis would be the harder and more dangerous fight. He's bigger, stronger, and hits harder than Ali, and he has tools that could definitely trouble Usyk, his inside fighting, body work, and uppercuts. Ali really only has speed, and aside from that Usyk does almost everything better. Lewis has the tools to be dangerous throughout the entire fight.
It would be easier for him to lose to Ali, Lewis threw body shots and his right hand like the one on Rahman could carry some CTE with it
This is a tough one. It's hard to go against speed. I'll pick Ali. LL had defensive lapses before that have cost him the fight. I think Usyk probably has at least the same power as a McCall (at least). I think he might be aggressive since he has beaten bigger men (Fury & AJ).
Both in their primes would be tough for him for different reasons. I have to give Lewis a slight edge as with his size and power advantage he was also fast and skilled enough to get to Usyk.