https://screenrant.com/cobra-kai-terry-silver-best-fighter-show-reason/

Cobra Kai is full of skilled martial artists, but none are on the level of Thomas Ian Griffin's Terry Silver, who can beat all other characters.

Silver lasted longer against Mr. Miyagi than Kreese did in KK3, and he was able to beat Johnny (who was an even match with Kreese and even got the better of him at some points) pretty easily. I'd definitely say he is the best fighter.