This achievement is pretty easy to do. Select Taki and do her Unblockable attack Ninja Cannon Fury (Forward+A+B) over and over again. this video shows just one fight, but just keep repeating it on the other stages. Good luck!
Edit: You can't expect to get this achievement first try, I mean like I said it's not exactly a cakewalk. You'll get frustrated with the apprentice, but just keep at it, it took me I think 3 times to complete the achievement so I was on the same boat as some of you.