Fracture

A very simple way to get this is on Act 3: Take Down The Dreadnought.

When you drop down into an area and the comms guy says 'Meet up with the Dev Team' (the area has a slanted building on your left that's fallen over creating a triangular roof) there is a Mole Mine to the left of you and about a dozen enemy turn up.

Kill as many as you want then die, you'll respawn right next to the mole mine. Continue until you get 25 kills, this may take 4 or 5 goes.



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Thanks to LosersVoteParty for help with clarification.

You can also do this in the weapons test, although you will need 80 data cells to unlock all weapons and 100 data cells to unlock the tdv in weapons test mode. All you need to do is equip the weapon and step on the red circle for a little and that will spawn enemies...kill the enemies with the weapon, it will unlock after you get 25 kills with the mole mines.

Getting this in Weapons Testing mode is far from obvious. A lot of the weapons are in plain sight and maybe you have to find so many data cells to unlock them, but the Mole Mine is locked away behind the force field that is on the far side of the map (opposite of where you spawn). To bring down the force field, you have to destroy the generators on either side of the force field. To destroy the generators you have to...
1) use Terrain Deformation to tilt the giant cannon vaguely in the direction of a generator. The "cannon" is the massive pipe in front of the four colored circles just downhill from where you spawn.
2) "Load" the cannon by standing on the dark blue circle to make crates fall into the large, light blue circle, then step into the yellow circle to suck them into the cannon.
3) Step into the green circle to make the cannon fling the crates in the direction of the generator. You don't have to be very accurate, because it isn't very accurate.
A crate is bound to hit and destroy the generator. Repeat the process for the other generator. You can now go through the passage and collect the weapon. On your return to the wide open area you'll find that some of the tougher enemies have automatically spawned. You might find it easier to destroy them with a more convenient weapon, then hop onto the tower to spawn mostly weaker enemies below. I had to make a couple of trips to re-load the Mole Mine gun.

To get this achievement, all you have to do is get 25 kills with the Mole Mine weapon. All kills you get will count towards the achievement. You can find this weapon in Act 3 when you are told to "Deliver the charge to the dreadnought". It is in a house on the 2nd floor when the dreadnought is firing beams down.