Mechagodzilla 3: Easy Wins:

Press Away + A then hold Black + White once they are off the ground from the first hit. If you win a beam fight, immediately afterwards tap R. Make sure to use beam attacks once in a while. Tail, fist, and booster attacks are good combos to do some damage. When you get the chance, grab and have him use the eye laser. It is good for a grab attack. Repeat in any order desired. Use circle sweep for a good knock down, but jump back for dodging the ground recover moves that your opponent does.