Achievement
Charge-Up Trainee
Points Awarded: 5
Fire 10 Charge-Up Attacks.
Tips
Just gather enough ammo, then hold down one of the weapon buttons until you reach level one or higher and let loose. As far as I'm aware, you don't have to hit anything, so this is another pretty quick achievement.
Also, but unconfirmed, you can add to this total by pulling off combo moves via the D-pad, old school style.