Yeah, the fight scenes were crazy insane awesome, and the ruthless, merciless, assassin Raizo wields his chain-scythe like a demon incarnate, with dizzying martial arts and acrobatics. But what enhanced all that was the script writing, and the acting of the lead. There was enough back story told through well-paced flashbacks to really make you care about the character and his dilemma.
Rain is believable as the dark, disturbed killer who had recently broken away from his clan. He's captivating on screen, and anchors the audience's eye.
And it had humor. Always a plus.
It was mesmerizing from start to finish. There was lots of blood, but it was the cocktail of story, acting, and action that merited 5 stars for me.