Does Usyk's last performance affects his ranking on an ATG heavyweights list?

No, if a fighter is truly exceptional, it evidently doesn't matter all that much. Did Joe Louis suddenly age between fights with Billy Conn? Did John Ruiz age from one fight to the next against Roy Jones? Did Evander Holyfield suddenly age between fights with Michael Moorer? Did Rocky Marciano suddenly age between his fights with Moore and Charles? Keep trying...

And remember, Leon Spinks was an Olympic champion with only seven professional fights under his belt—since you seem to have forgotten than

 

I don't personally find the Ali loss to Leon to be too bad. It was included because it comes up.

As for Homes--RUBBISH. Holmes hand-picked Spinks to win his 49th on the basis that there was no possible chance of him winning. Holmes OPENLY bragged about it, telling Spinks he had no chance as his jab would feel like a LHW right hand. People either don't know this or don't want to remember, but BY HOLME'S WON METRIC, and by the reaction at the time, it was profoundly humiliating. It is one of those things where over time, a narrative has developed that it isn't that bad, but it was at the time, and really still is.


“I want a lot of money and no more of those big hitters like Tim Witherspoon and Mike Weaver,” he told Pat Putnam of Sports Illustrated. “I’ve paid my dues and if they want me back, they’ve got to give me little people I can beat on without getting hurt.”

From Spinks:
''He told me his jab would feel like a light heavyweight's right hand but it felt like a lightweight's right,'' Spinks said. ''It was nothing. Ali had told me to stay away from Larry for six rounds because his legs couldn't take it after that. But I didn't see how I could run. I intimidated him by standing there and giving him head movement.''

Even Spinks didn't believe it was possible:
''I never had a feeling I'd win,'' he said. ''But I decided to do my best and let the better man win. And believe it or not, the better man won.''

From an article after the win:
https://www.nytimes.com/1985/09/23/sports/spinks-is-giddy-with-success.html
Spinks survived. Now, he has fought his way to the heavyweight championship that the boxing experts gave him virtually no chance to win.

From a 1985 article:
https://www.thefightcity.com/sept-21-1985-holmes-vs-spinks-boxing/
After all, no light heavyweight world champion had ever succeeded in taking the heavyweight title. Such legendary Hall of Fame pugilists as Billy Conn, Archie Moore and Bob Foster had all tried and all had failed, and no one was yet talking about Spinks in the same breath as those former greats of the 175 pound division. Moore himself compared Holmes vs Spinks to a smash ’em up derby between a transport truck and a Volkswagen.

From New York Times:
https://www.nytimes.com/1985/09/21/sports/spinks-at-200-for-title-fight.html
During the week, Spinks managed to create more suspense over the weigh-in than there was about the outcome of his fight against Holmes Saturday night for the International Boxing Federation heavyweight championship. Spinks is attempting to become the first light heavyweight champion to win the heavyweight title and his chances were considered the same as his nickname - ''Slim.'' That still may be true, although no one will be calling Spinks slim any more.

https://boxing-social.com/features/michael-spinks-my-two-fights-with-larry-holmes/
Virtually everyone outside of Spinks’ inner circle had written him off. With Holmes chasing history-making records, Spinks had history against him. But Spinks had moulded his physique into a viable heavyweight contender. Veteran trainer Eddie Futch had connections to both fighters, Futch stayed neutral and at home.

 

Leon Spinks ultimately had 17 losses and was knocked out by Gerrie Coetzee in 2 minutes. That's not exactly elite level.

 

People underestimated Spinks.
How do you respond to the examples I gave? Why the hell am I even doing this?
Billy Conn was a light heavyweight who gave Joe Louis his toughest fight; did Joe Louis suddenly age overnight like Usyk and Holmes did?
Dismissing arguments isn't a counter-argument.
I found several light heavyweights who successfully competed at heavyweight, yet you keep looking for kickboxers. There were a few of them—Roufus, Dorsey, Piotrowski, Le Banner, Bush—but which of them would have posed a problem for Bowe, Lewis, Holyfield, or Klitschko if he had made his debut at age 37?

 

Spinks suffered a terrible slump in form; he was a "Mike Tyson before Tyson"—a notorious party animal who had lost interest in boxing. Do you really think someone who wasn't elite-level could have won an Olympic gold medal in such fashion? His older brother was always considered the better of the two.

 

Because he had to gain nearly 30 pounds and beat a supposedly great champ. Yeah, people underestimated Rico. But Usyk beat a kickboxer and Larry lost to a career LHW.

 

A "terrible slump in form" - at age 26 after giving Ali two of his toughest fights... Leon was also 200 lb and smaller than Ali.

And he didn't win olympic gold at heavyweight, did he?

 

If you don't train, you can experience a drop in form at any age...
Do you think Rico has a shot at the next Olympics? Honestly, it surprises me that so many outstanding kickboxers tried their hand at boxing but couldn't win any belts—take Rick Roufus, Rob Kaman, or Peter Aerts, for example... Do you think Roy Jones or Holyfield were lucky not to face them in the boxing ring?

 

This example is strange. For the second fight, Spinks didn't need to put on any more weight, and as we know, Holmes was aging with every fight—like Usyk against Rico. How on earth did Holmes perform better in the rematch? Did he reverse the aging process? Did Spinks age instead this time?

 

I don't consider Usyk an ATG.

Good yes but not great!

 

The second fight has nothing to do with anything. You are grasping at straws. At the end of the day, Holmes got beat by a guy coming up two weight classes, and everyone knew it was humiliating--most of all Holmes. If you don't know this, do some reading.

 

You can give the same excuses for Usyk too. He didn't train properly, didn't take Rico seriously, and so on and so forth. He's also 39 and didn't have any footage to study, unlike Rico.

Aerts and the others didn't have the same experience and trainer Rico's got. Rico's been sparring elite heavyweights for 15 years or so with Peter Fury as his trainer. Another Kickboxer who transitioned well was Paul Briggs

 

huh? You are really counting Amateur fights which are light work? lol Rico has had 70 pro kickboxing fights vs Usyk 25 pro fights., and everyone knows the wear and tear in kickboxing is leagues higher than boxing. Rico has far more miles on the clock than Usyk.

The excuse of getting old overnight does not apply to fighting a kickboxing rookie who is basically just as old as you. Near 50 year old Foreman and Holmes was still beating top pros let alone rookie kickboxers. He should have outboxed him with 1 hand tied behind his back.

 

That is one of the dumbest things I have read on here. You think a losing to a pro boxer coming up 2 weight classes is worse than getting outboxed and almost losing to a kickboxer on debut basically in boxing? That's laughable. The former is still an experienced pro boxer, the latter isn't