List of Weight-Drained Pacquiao Opponents
Erik Morales 2
Erik Morales 3
Oscar De La Hoya
As far as I know, these are the fights in which Pacquiao's opponent was weight-drained. All you have to do is look at the fighter's boxrec page and check the weight he was at in his previous fight.
Did I miss any fights, or is the list complete? Notice that those are Pacquiao's most impressive wins, except for Hatton and Barrera 1. His resume is all smoke and mirrors. Freddie Roach managed him well.
Erik Morales was only stopped twice in his career, both times being in the two Pacquiao rematches, when Freddie Roach forced him to drain himself for a big payday. The only time he fought Pacquiao on even terms (in the first fight), he beat him.