Both Usyk-Fury fights were relatively clinch free. Not because Fury didn't try but because grabbing Uyk doesn't really work. He's got ATG clinch avoidance skills. Grab him, he wriggles out and shoves. And he must be one of those guys who is stronger than he looks, because he was able to do it to even AJ, and AJ looks like a colossus next to Usyk.
Usyk also utilises being the shorter man - I noticed he also ducked under a number of attempts made by Fury to clinch him - pivoting at the same time, seeing him end up being to the side of Fury and sometimes very near behind him. Though, in the rematch, there was at least notable moment when Usyk exercised sheer strength shoving Fury off him and into a corner. I think Usyk is respectably strong in sheer terms. Regarding body weight again….some are equating greater body weight to likely greater strength - but perhaps greater weight is also the crux of a false positive. Suppose hypothetically it appeared that Fury and Usyk could shove one another around in equal measure - that wouldn’t equate to equal strength since quite obviously Usyk has more to shift when his opponents greater body weight is also accounted for. When Johnson fought Willard, while Jack wasn’t able to shift Willard as easily as he did others, the bigger Willard himself wasn’t able to shift Johnson - at least up until Jack began to flag. So, just imo, that was Johnson still showing off his notable strength against a guy approaching the SHW class.
Not any specific fight but I’ve noted that Liston didn’t clinch much if at all. Several opponents tried to clinch him, however, hanging on for dear life - if one of Liston’s arms was taken up by same, he simply wailed on his man with the other hand. I see Liston as a very clean, open fighter in that regard. As far as I’ve seen, Joe Frazier wasn’t prone to clinching either. No mucking around. Joe just came to punch, punch, punch and knock his opponents block off. Very honest fighter - though, he was the victim of the one of the worst, express clinching strategies when he faced Ali in their rematch. Tua - Ibeabuchi was a punch fest, not a clinch in sight or barely. A crazy, I’ll punch you then you punch me fight. That single fight had to have taken quite a bit from both men.