Henry Armstrong's wins against Barney Ross & Lou Ambers Ezzard Charles's wins against Charley Burley in 1942 Muhammad Ali's wins against Fraizer & Foreman Maybe Kid Gavilan's wins against Ike Williams in 1949 (although I read that result of their 1st fight was controversial)
If you are allowed to count same-guy contests, it's going to be Zivic beating Armstrong back-to-back in 40/41. People try to diminish these wins, but Zivic clearly had the edge on Armstrong in styles, Armstrong just couldn't cope inside. Armstrong wasn't prime, but he's arguably the single best fighter of all time, had lost something like one fight in 50 and hadn't been stopped since his debut (from memory). They are incredible undervalued wins.
Yes, "same-guy contests" are allowed. I included them in my OP too. Zivic-Armstrong is an excellent pick. Edit: Actually, Zivic had three fights before his rematch with Armstrong, so that one doesn't count.
Nice thread idea. Of those you cite, Armstrong's is probably the greatest. Burley was smaller than Charles, whereas Ross was bigger than Armstrong. Frazier and Foreman don't rank as high on p4p lists as Ross and no higher than Ambers. Williams was a natural LW vs natural WW in Gavilan. Other notable include: Terry McGovern's wins over (admittedly a slightly fadded) ATG FW George Dixon and the much bigger borderline ATG LW Frank Erne. From a p4p perspectives: The 5ft 7ins natural WW/MW Mickey Walker's B2B wins over HW contenders King Levinsky (23lbs heavier) and Paulino Uzcudun (27lbs heavier). The 105lbs Jimmy Wilde over FW contender Joe Conn and ATG BW Joe Lynch. Can you imagine a fight between a Minimumweight and FW contender even being sanctioned today?!? Sam Langfords B2B wins over the 37lbs heavier Sam McVea.
Sam Langford also KO'd Harry Wills (7 inch difference in height) and defeated Sam McVea B2B in 1916 .
Pacquiao beating Barrera (2) and JMM (2) back to back is pretty impressive. Andre Ward beating Carl Froch and Chad Dawson back to back is also worth mentioning as well.
Maybe not the greatest but Marvin Hagler's back to back wins over Tommy Hearns and John Mugabe deserve an honourable mention.
Another hounorable mention would be Usyk beating a dangerous contender in Dubois followed by a unifying the heavyweight championship vs Fury. My overall pick is probably Ali's back to back wins over Frazier and Foreman.
Michael Spinks's back to back wins over Marvin Johnson and Eddie Mustafa Muhammad are another hounourable mention. Also Carlos Monzon defending his title vs Benvenuti followed by Emile Griffith.