The Dragon Sniper was one of my most used guns in the game and I had about 500 kills with it by the time I got my Platinum. This gun is first found in chapter 3 and it is a scoped rifle, a sniper. It is one hit kill anywhere on the body, even on Crushing. The game has a lot of parts to it where you need to snipe enemies that are far away to protect your partner, so you will get this by the time you finish up your two playthroughs without a doubt. The trophy will unlock once you get 50 kills with it.