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