Saitama, Japan: Nonito Donaire said he was felled by "the hardest punch I've ever been hit with" as bantamweight king Naoya Inoue inflicted a sensational second-round stoppage on the Filipino veteran in Saitama.
The unbeaten Japan boxing great known as "Monster" scored his 20th KO victory in 23 fights to add the WBC title to his WBA and IBF belts in a breathless display of power punching.
In the pair's first, classic fight three years ago in the same arena, five-weight world champion Donaire fractured a bone in Inoue's face as the Japanese was pushed all the way before scoring a unanimous points victory.
But in Tuesday's rematch the 39-year-old "Filipino Flash" Donaire was demolished like never before in his storied career.
Just seconds before the end of an even first round, Inoue's lightning quick overhand right to Donaire's temple scrambled the senses of the future Hall-of-Famer and sent him sprawling.
"That was the hardest punch I've ever been hit with. I came up completely blank," Donaire said to fans live on his YouTube channel following the defeat.
"When I got hit I didn't even know I got dropped. I didn't see that punch coming at all because I was trying to counter him and got caught. That was pretty much it."
In round two a barrage of precision power punches from Inoue induced wobbly legs in the gutsy Donaire before a second knockdown saw the referee call off the contest.
Donaire had only been stopped once in his previous 48 fights.
He paid tribute to the 29-year-old Inoue, regarded by many as the best pound-for-pound puncher in world boxing.
"He's an amazing fighter and I'm glad I got to share the ring with him," said Donaire.
"Inoue got me really good and I'm glad the referee stopped the fight as I was always going to stand up - I just don't have any quit in me.
"It is what it is. I'm only grateful that I'm healthy."