Aliens Colonial Marines
60 Achievements
1,250
35-40h
Arbitrarily Exterminated
Kill 2179 Xenomorphs
30
How to unlock the Arbitrarily Exterminated achievement in Aliens Colonial Marines - Definitive Guide
I was getting 20-30 kills every few minutes and it popped after about 20-25 minutes. Remember though this is after I did everything else to minimize the kills I would need.
Might not be the fastest but worked for me
You can also spawn 1 more alien by going in the room on the left just over half way up the corridor tunnel
there is NO way to track your progress other than counting yourself but just keep shooting it will unlock as soon as you kill the required number xeno
Reloading the checkpoint does not reset your kills to where they were before - hope this helps
After you have destroyed all the AA Guns and get to the section where you drop down and have to run from the Queen.
DON'T DROP DOWN!!!!
To the right and front of the platform is a few stacked containers.
There is an infinite Xeno Spawn here!!!!
I was able to get over 200 kills before exhausting all of the ammo on my weapons(not shotguns). Once you run out of ammo you can reload the checkpoint and run it again.
Side Note: I also farmed over 3000 XP by the time the achievement popped.
After completing the game on recruit, UBA and finishing challenges, load up mission 4 (No Hope in Hadley's). When you first get the SmartGun, start killing in the tunnels and restart checkpoint when it's cleared out. You can get about 20-30 kills every few minutes. This seems to be the fastest method so far.
This trophy is cumulative and will come over time. All kills earned both Offline and Online will count towards this total. Unfortunately there is no way to check your total kills but if you don’t have this before finishing everything else, then there is a good spot in the campaign that allows you to rack up a fairly decent number of kills in only a few minutes.
Play through the fourth chapter, No Hope in Hadley's, on Recruit difficulty up until the point where you acquire the Smart Gun. The long corridor area contains at least 30 Xenomorphs that can be killed very quickly with the auto-tracking feature of the Smart Gun. Make your way to the end of the corridor, ensuring that you kill all of the Xenomorphs, then restart the checkpoint. All of your kills will carry over and you'll be able to go through the corridor area with the Smart Gun again. Just make sure that you don't accidentally trigger the next checkpoint and you can repeat this process for as long as necessary. As a guide, I restarted the checkpoint as soon as O'Neal tried to reach the other Marines on the radio. Thanks to Shakey for testing and confirming this.