Vortex Volley All starting Titans will have this shield, it is the first load-out titan you can pick when you choose Titan load-out pausing your game when you are in a match.
This achievement is quite simple, to use the Vortex shield you must hold LB, while firing at the enemy if you see them using the shield, just activate your shield and wait until he/she fires into your shield, and just fire back, achievement unlocked.
Video: Great job getting it done by GameInfirmary.
Good Luck and have fun!