Setup a VCTF to 1 capture with novice bots and on any map in multiplayer. Before starting your game change your character in the main menu to be Axon. Then when setting up the match make the bots Necris. When in the game use all the vehicles on your team (killing at least 1 enemy in each one) and finish the game. In the next match do the same again but change your character to Necris and the bots to Axon. Keep repeating this method if you don't get the achievement straight away as you may have to go to a few different maps to have access to other vehicles and turrets. You can look if have killed someone in a vehicle or turret in your stats. You can't run them down as it doesn't count.
Axon and Necris vehicles are:
Turret (counts as a vehicle so use it!)