Giving away a lot of size against Donato Paduano, he looked great in that fight. Beautiful skills. In the re-match with Frankie Otero he was dominant and boxed beautifully too.
I'm not sure if it's his absolute best, but I think his win and performance against Jim Watt is very underrated. Watt hadn't made it to world class status yet but it was a very technical fight at a high standard. Buchanan showed great adaptation to turn it round in the last few rounds with his inside fighting and body attacks.
I love the fight. Definitely one of my favorite Buchanan fights and Buchanan is one of my favorite fighters.
I would say his title-winning performance against Ismael Laguna. He was not only fighting a speedy master boxer, but the Puerto Rican heat which he was unaccustomed to. Brilliant.
All good and valid answers thus far. I'm partial to him setting his feet, standing his ground and uncorking his underrated right hand to show the more ruthless and spiteful side of his game in taking out the undefeated Chang Kil Lee in a couple of rounds. Lee was the Orient champion who had beaten Ishimatsu as well as future title challengers like Furuyama and Tsujimoto and went on to challenge Cervantes. A very good and underrated win for Buchanan.
Buchanan is difficult... He's the borderline between great and really (or all-time) great.. I'll say Laguna was a wonderful showing!
Beautiful boxer. Rallying from a cut eye and poor start to stop the top notch Carlos Hernandez deserves some credit imv. Ken really sat down on his shots late here probably more so than any other fight of his. It showed he had the grit to match those beautiful skills.