For this achievement you need to do a character specific Tag Throw. For this I picked Devil Jin and Kazuya. Their special Tag Throw are the Mishima headbutts. You'll know you've did it right when after your first character headbutts the opponent your second will then grab the opponent and then headbutt them again.
The Tag Throw will go like this: , + + , (Or , + + , depending on what side you are on). If you were successful do it two more times.
Another Tag Throw is with Baek and Hwoarang. Press , + , and both of them will come on screen and do a flurry of kicks to their opponent (Thanks to demonocracy for the tip).
NOTE: This can be done in Practice Mode.