The easiest way to earn this achievement is to repeatedly perform the Panda Quake attack (jump then press B in the air).
If you have fully upgraded your Panda Quake attack, reload the first level and when you reach the big fight at the end, wait until you have a lot of enemies around you and then just pound away and the jump and B buttons. Make sure you press jump as soon as you land otherwise you won't be able to get the next hit in before the combo ends. I managed to get a hit counter of almost 30 using this method. It's cheap, but it works.
Also, make sure you have full Chi, or are using the infinite Chi cheat otherwise you may run out of Chi whilst trying the above method.