Who would you say is the greatest southpaw(s) of all time?

[Master]

Whitaker
Pacquiao
Hagler
amazingly enough although not the greatest southpaw Moorer has to go down as one of the best, he was an amazing fighter before moving up to HW

Moorer was a vicious puncher at light heavy but did not challenge the best fighters at that weight to be considrede amazing.

Segio Martinez has done better.