Your Void Reactor needs to be Level 5. Go into challenge mode (new game+) and proceed to the area where you first meet Ms. Zurkon. Buy ammo from her so you're topped off on Void Reactor. Move ahead to where you first learn to void jump and this will be your grind checkpoint. Kill the first enemy that flies in on the ship and void jump up. On the far end of this courtyard, a dropship will unload four goons and then unleash a pack of robo dogs. Run forward, use the Drillpack to weaken the goons, then back up. Pull out the Void Reactor and hold L2 to open the shield. You'll see enemy shots stick into the shield as pink/purple spots, then when you pull R2, the pink/purple beams will return. Keep catching shots and returning them at the dogs/goons until you run out of ammo and repeat checkpoint until you've got your 10 kills.