You'll easily make a dent with this achievement if you are working on the "Zeus" achievement (win 500 games), but the fastest way to get your kills in is setup an Online Hosted game, kills to 15, respawn time to 0 and add your alt/doublebox!
Now just keep grinding your 15 kills, Use the "same map" voting option, and repeat until the achievement unlocks! This took awhile, but if you are tackling the other "win" & "ranked" achievements, you'll make a lot of progress. I actually unlocked this before I hit the Zeus achievement just from all the other achievement requirements.