To get the trophy that's called "Sabre Rattler", you must have Axhind kill at least 100 enemies with his special skill, the Sabre turret.
First off, if you haven't done already or if you're playing for the first time, chose Axhind, the soldier, as your new character and start up the new playthrough.
Next, make sure to take out monsters and complete missions in the Southern Shelf and in Southern Shelf bay until you reach level 5.
Once you've reached level 5, go into your skill tree menu and unlock the Sabre Turret.
From this point on, it's really just a matter of finding some enemies nearby and unleashing the Sabre turret by pressing
. Axhind will taunt them as he throws it out onto the ground, so the carnage should begin.
Repeat this process again and again as you see new baddies to take on until at least one-hundred enemies have been destroyed by the Sabre turret and the trophy should unlock for good!
Good luck, have fun, and happy hunting!