This Seeking Tech video guide will show you how to get the Zack the Sniper trophy and achievement in Crisis Core: Final Fantasy VII Reunion.
This will unlock when you do the following:
Did not allow a single gun bull head to escape while sniping.
As always, save your game before you attempt this trophy as you only have one chance to get it right.
You will need to grind when you start to encounter random enemies in order to earn Kill Points. You will need at least 70 to maximum the strength and aim of your rifle, while also having enough to buy smart bombs.
You can find the full video walkthrough for this trophy below: