To defeat Grevious without being hit use force push to push him as far back as possible. Then wait for him to jump. After he jumps he'll flip backward. (like he should) When he flips run tword him don't stop until you hit the other end of the screen, and don't hit him either. Then if he jumps he'll flip off of the screen then he'll walk toward you, but he can't walk back on the screen. Then keep using Mind trick until you confuse him. (He'll point his lightsabers on a downward slant then hit him) He can't hurt you off the screen. This isn't really important. So don't get discouraged if it doesn't work. It takes a lot of skill, but it works for me.