See Instruction from the game

One of the main attack methods is the headstompter. After killing a ninja you can jump its head and make their brains pop out. Then you can use the brain as a football and hurt other ninjas with, of course nobody but chuck norris would think of something like that! You can also rip enemies hearts out and eat them to gain more health points. Be sure to use chucks supreme fighting skills and using the roundhouse kick. Other than that just go out there and kick some serious ninja butt