The Filipino legend lost to Bradley in controversial circumstances two years ago and is out for revenge.
Pacquiao wants to prove all his doubters wrong and return to the pinnacle of boxing.
"There are a lot of people who doubt I can fight the same way I fought when I knocked out Oscar De La Hoya, Ricky Hatton, Erik Morales," Pacquiao told The Telegraph. "I want to prove to them that I am the best.
"This is the first time I have challenged for a world title that I lost. Do I want it back? You bet I do, and I want it back from Tim Bradley. The only way Bradley can beat me this time is to knock me out. He cannot outbox me.
"Last time I was too nice. This time I will finish what I start. I want to get back that belt he won off me. This is a mission to prove I am the best."
Pacquiao takes on Bradley for the WBO welterweight title in Las Vegas on Saturday night.