Just play the first level and put on easy, punch. Forget kicking because I learnt if you start kicking then the opponent tends to block more often, punching is easier to break through the barrier plus it will give the person more time to react a lot more commonly to your attacks if you kick.
Also make sure you decrease the timer, etc... so it's over quickly. This should work on most opponent's except maybe metal sonic where he will throw you up frequently if you get close
Also set barrier's to 1, this is best done in the earlier levels.
Oh, to the people thumbing down have the decency to explain why you had problems with this solution.
This might as help you get this achievement too: