Things like strength, punching power, chin, height/reach, speed, reflexes etc... I'll start with Mike Tyson. Altough some say he was a small heavyweight, he was mostly stronger then his opponents with greater punching power. He was short for a heavyweight with a short reach, but was genetically blessed with other things like strength, punching power, great chin, good reflexes, speed (hand and foot)... Ali had it everything except great punching power..
I believe Henry Armstrong’s abnormally large heart, which was 1/3 bigger than the average heart, makes him the most genetically gifted athlete.
Deontay wilder is a example of a natural athlete, he doesn't even run but has 12 round stamina. George foreman is probably the most naturally gifted out of all of fighters, he had size, one of the hardest punches, and probably the best chin of all time, if he wasn' he wouldn't have been able to come back as an old man and knock out moorer. Max Baer is another naturally gifted fighter.
Deontay goes quite a while during fights not throwing because he`s crap at dealing with god counters, he relies on his reach which makes him gifted in that regard and jabs a lot, jabs don`t take much out of you the only other punch he really throws is the right hand a bit like Frank Bruno but he just does it much better.
Mike Tyson was surely. Ike Ibeabuchi too. These two genetic freaks. Bowe was extremely gifted in that sence that he didn't look like Ike or Mike, but he had punching power, size, and endless stamina (even though he never trained as hard as Holy, he had better stamina)
Strength and power foreman Speed and reflexes jones and clay Stamina rocky ,frazier and a lot of the old school era Toughness chuvalo,hagler, lamotta Every guy had his part
I don' think he's in the top 100 most skilled fighters, but he has natural power that you can' teach, tall and rangy, naturally athletic build with amazing stamina that he doesn' really need to work on accord8ng to himself atleast
Sonny Liston comes to mind. He was about 6-1 but he had an Uncommon reach of about 84 inches reportedly. By most accounts he also had hands the size of hams. At 212-215lbs he was a powerhouse. Just a freak of nature. Looking at pics of Liston he would appear to be a 230lb or more heavyweight.
If you're just talking natural athlete's then aside from those already mentioned, and outside of obvious great boxers, then David Haye I is worth a mention. Never a great boxer, but definitely a great athlete