22 Aug 2012 22 Aug 2012
This is quite easy in Arms Race. You can do this offline vs. easy Bots. It maybe working on even lower difficulties, but I'm not sure about that it, as playing on the lowest difficulties do not count towards awards so that may be the case for achievements, too.
If you kill the same enemy multiple times without being killed by him, you dominate that enemy and get the achievment.
Arms Race is a game type with ifinite respawns. Each time you kill an enemy, you get another weapon until you have to perform a knive kill to win the game (Like the popular gungame mod for Counterstrike:Source on PC). The Maps for Arms Race are pretty small. Combined with the respawn system, this results in a constant flow of enemies.
On Easy difficulty, Bots mostly stand around near their spawn point and look at you instead of firing, so it is easy to kill them. Just run through the map and visit the enemy spawn a few times and it will pop.