Again, you'll get this one while going for The King of Fighters achievement. You must beat one entire team with one of your team members. If you're having a tough time, practice with one character and get decent with them. It should come easily.
Note: To make these easier, make sure that you do the following in the Options menu:
Set the difficulty to 1 (Easiest)
Set your players power gauge to MAX
Set your defence to level 8
Set CPU's defence to level 1