Mayweathers obviously - They literally built Floyd. Floyd was a born and bred fighter trained under the tutelage of his uncle and father.
Shingo Inoue deserves a shout here. He has built his two kids from scratch, heck he even built the gym that they trained in as amateurs. Within 3 years he has gone from an unknown to being the trainer of 1 world champion (a 2-weight one at that) and one world ranked guy.
Mayweather Sr is actually an underrated trainer. He guided a young Chad Dawson and Guzman to become great champions at their respective weight classes.
Mike Stafford. Developed Broner into the fearless fighter he is today.He don't need protection. Shout out to Calzaghe dad for creating a fighting style of combining slapping,wind milling,and cocaine together to make his son outlast old fighters.