Easiest method is to play with Chie.
Start up a versus match against an AI or another local controller, and build up enough meter to do 2 supers (4 on the bar)
As Chie, use your down-to-back
+
to use a power up super and immediately follow with a down to forward
+
to bring down the giant fist.
The opponent should now most likely be defeated, and the achievement should unlock.