If you don't consider Wlad to have one of the best 1-2 you don't really follow boxing. The clinic on Chagaev is incredible. His inside game is none. His clinching is too much, but punch for punch at range there aren't many better.
Frankie Randall - against Sammy Fuentes and JC Chavez I and II. Roger Mayweather in many fights. Matthew Saad Muhammad against Pete McIntyre and Richie Kates and Marvin Johnson II (7th round).
Ali by a mile. Perfectly thrown, perfectly timed, quicker than anyone could throw it. Look at Ali Williams for his best examples.
Lennox Lewis for power and speed ezzard Charles should definitely get a mention in this category ali sonny Liston wladimir should get a mention in here too