Resonance of Fate

Personally i found this achievement easy to use a MG person whoever yours is, mine was Zephyr.

To get a bonus hit, press (X) to go into hero mode, while running keep shooting the target and you might hit him in the air. When you keep attacking him while the enemy is in the air you will notice a yellow circle starts to form. After the circle is filled a little you will get a chance to press (A) if you land on the yellow part you will stop running and your character will aim at the enemy. Before he hits the ground press (A) again so you start shooting him this is a bonus hit that is complete. If you fail to hit him it will not count towards the achievement. To check the amount of Bonus hits done goto the Arena and check the board at the front desk (Game records and look under Bonus Hit Count) you need to do 100 to unlock the achievement