Quote (Magistick @ Dec 18 2012 07:43am)
I heard haki nullify devil fruits power, I might be wrong though..
There's 3 hakis. I dont want to explain all of them so look it up yourself.
One of the hakis (Busoshoku) basically gives you invisible armor. So basically they can fight people like Ace, or Akainu. However, the Busoshoku can also be used to attacks. It comes out stronger obviously. For example Amazon women who use their arrows use Busoshoku Haki to power them up.
As for Luffy hurting the other guy, Its possible Luffy didnt use any Haki on the first part. And like the other person said. Fillers make them look weak =\