For one punch power I would put it in this order: Pacquiao Barrios Valero Soto Guzman Juan Diaz David Diaz
I think Valero gets these KO's against C/D levels moreso because of his ultra-aggressive style and desire to win by KO than anything else. His power is obviously real on some level, but it hasn't been proven at all and he still hasn't even faced or stopped a B level opponent.
I can't vote yet for Edwin even with his good resume, He needs to fight bigger names. I would like Guzman or Soto first.