The best advice I ever heard from a trainer was. "I told you to get out there and hit him. NOW GOD DAMMIT GET OUT THERE AND HIT HIM !"
i kinda like john david jackson his technical advice is always good plus he can even make cliches sound menacing: "you've taken him to deep water, now you gotta drown him!"
I think of 4 listed its Mayweather snr, with Roach as close second. By the way does Roger Mayweather train anyone right now? I would guess since Floyd retired, Roger would be popular choise for upcoming stars to get known :huhUnless Floyd will soon get back in the ring.
IN that case out of the 4 I would have to say Manny Stewart. He has trained movers,boxers, punchers and could train and adapt a fighter to fight different styles and isn't a master at just one style like Mayweather sr. (boxers) and Roach(agressive fighters). He has also developed more fighters which is much more impresive for me although i feel he has slipped a bit.