Gene Fullmer by "Sugar" Ray Robinson with a left hook which many call the greatest punch ever thrown. Robinson decked Fullmer with a left hook directly on the chin on the way in and Gene went down and rolled around on the ring attempting to get up but couldn't make it back to his feet before the count of 10.
You can check it out here @ 8:51 of this vid. [yt]rdROjwy34qU[/yt] Afterward Fullmer walked back to his corner and asked why Robinson was celebrating in the middle of the fight? Fullmer's cornerman actually had to explain to him that he'd just been knocked out.
Don't you know anything? Any boxer who has ever been knocked out even once is a glass jawed mega fraud. Sheesh! atsch
Being as that Duran had already been dropped twice in round 1, and that he was already hurt and "fighting off instinct" as the commentator said, I don't really consider Hearns-Duran a one-punch KO. But for others good-to-ATG fighters who were stopped by single punches: Sumbu Kalambay by Michael Nunn Dick Tiger by Bob Foster Ezzard Charles by Jersey Joe Walcott Jersey Joe Walcott by Rocky Marciano Donald Curry by Mike McCallum Gene Fuller by Sugar Ray Robinson Herol Graham by Julian Jackson Marvin Johnson by Michael Spinks Welcome Ncita by Kennedy McKinney Then you have other cases where the guy gets up, but the fight is as good as done, and the fight ends shortly after that: Michael Nunn by James Toney Marco Antonio Barrera by Junior Jones
Duran - Hearns wasn't a true one-punch KO though. Duran went down twice in the 1st round and was already badly hurt in the 2nd round before the fight ending right hand landed.
Manny Pacquiao was taken out with one punch by Rustico Torrecampo. Rather than just get taken out with a perfect punch, Archie Moore was instead dropped six times against Jimmy Bivins and five times against Eddie Booker. What a couple of glass-jawed jokes.