tyson vs. Buster Douglas is a strong possibility?
Or Ali - Liston?
…
Lewis v Rahman
Cuz Rahman has always been terrible, he got 1 lucky punch
if ur talking about odds then judah baldometer! is the biggest recently.
it’s Boldizar
SRR-Turpin
its baldomuffin 
biggest upset by betting odds i think = tyson douglas
…Perhaps not the biggest - but some that stick in my mind
Honeyghan v Curry
Holyfield v Tyson 1
Spinks v Ali
Ali v Foreman
Foreman v Frazier was a biggun’ too.
Tommy Morrison-Michael Bentt
Oliver Mccall-Lennox Lewis 1
George Foreman-Michael Moorer
Terry Norris-Keith Mullings
Tyson-Buster Douglas
Tyson-Douglas
Leon Spinks vs Ali
Douglas was at least 35/1 to beat Tyson
Other huge upsets
Holyfield/TysonI
Honeyghan/Curry
Ali/SpinksI
Ali/Foreman
Liston/Clay(Ali)I
Braddock/Baer
Louis/SchmellingI
and believe it or not Johnson/Jeffries was (betting wise), probably the biggest upset in boxing history before Louis/SchmellingI