-An easy way to defeat any enemy is to not use any weapon. Raziel is faster on his feet, and his attacks are quick. It takes about two minutes to defeat the Fire Demon by doing this. Using the Soul Reaver for one or two strikes is not bad. However, make sure to finish it off barehanded to see Raziel go by its head, take hold of the horns, and twist its neck.
-To kill something fast, the best way is to use the Reaver. After charged it is extremely powerful and can, at the correct level, kill a Black Demon with two or three strikes. With a solid weapon or the claws, hold AUTOFACE and wait until the enemy uses a strong attack (when the weapon has a yellow ball, etc.). Press JUMP while pressing LEFT or RIGHT. It may be slightly tricky, but if used correctly you can do a good combo in your enemy's back.