How exactly do you think Mr. Miyagi killed Claramunt?
The series only told us Miyagi killed Claramunt on a Sekai Taikai match during the 40s or 50s decade.
But never the exact details.
My guess is that Miyagi and Claramunt were fighting evenly until Miyagi got the upper-hand and that made Claramunt become overly aggressive.
And Miyagi, in order to de-escalate Claramunt's aggression, ended up striking him a little too hard and killing him by accident when he just meant to make Claramunt surrender or, at worst, get unconscious.