Maybe Eubank Vs Watson back in the 90's. England had Eubank, Benn and Watson who dominated the middle weight class and in what would probably have been regarded as one of the greatest fights in history if there'd been an American involved, there was a terrible ending.
Eubank was losing the fight on points by a mile, he came out for the 12th in the knowledge he needed a knock out. He got it in true Rocky style, and although Watson didn't go down he later collapsed and fell into a coma.
He lived but is now more or less a vegetable