I like Cooney, but don't see what he has done to warrent his being included in a serious discussion about this topic, ditto Morrison!!! Best left hook I ever saw was SRR against Fullmer, best consistant left hook I have ever seen was Smokin Joe...I think Azumah Nelson had a nice hook as well!
Well it depends what "best" means. Are we talking speed, power, or accuracy? Frazier's was not that accurate but very powerful. He dropped quarry, staggered foreman, stopped Chuvalo, and knocked down Ali with it. Those should speak for themselves. However Tysons was accurate and very powerful, and he has a lot of KOs do to his hook. Morrison's was very compact, power, and clean. He could stagger anyone if he landed it. It was pretty fast too. Tua has a lot of KOs to his credit, and whenever he unleashes the left it seems like they are always staggered or backed off. So his left hook is very powerful, just not the fastest thing in the world. Sugar Ray Robinsons is fast, powerful, and accurate, so his would probably be the best. Leonards was good too but I wouldn't say its the best IMO. I would never count out Roy Jones Jr.'s either, his hook was extremely fast and he could throw many at a time. Nobody mentioned Evander Holyfields left hook, which at least deserves to be talked about. His left hook to the body was a thing of beauty. Dropped Mercer for the first time in his career!