Description of Achievement: Kill 200 enemies using only you dragon's secondary skill
Earn this in the Crimson Dragon Walkthrough.

How to earn this Achievement: Your dragon's secondary skill is your manual targeted fire (By default) which is selected by pressing LT, your recticle will change blue when selected.

Aim the recticle over enemies and press RT to fire, note this weapon has uses focus to fire so continued fire will deplete this bar in the top left so make sure to let it charge up between enemies, you may need to switch back to your main skill whilst it charges.

The 200 you need to kill counts all enemies though the larger enemies still only count as 1.