By "brutal", I don't mean "awesome"...I mean, bloody, furious, and deliciously violent.
My vote would probably have to go to Whitebeard Vs. Akainu...Whitebeard gets his face burned off for God's sakes! Also, Luffy Vs. Hody, and Chopper Vs. Kumadori (if only because it involved poor little Chopper getting thrown around like a ragdoll!)
I'm not gonna make a poll because there are just too many fights...what do you think??