Gamer has been removed
There are two methods to do this.
The first is for people who want these matches to count towards Annex:
Simply start up an Annex player match, 120 seconds for capture time, 3 rounds, and bleed out duration to 5 seconds.
Use a second controller / guest account as the team from the other side (sign in a second controller with the guest account and then you'll automatically join the match I think), have him spinning around or doing something. Then go and capture all the points until you reach 120 to win the round. Rinse and repeat.
Alternatively, you can do this easily in Warzone or Execution on this map. Set the matches to say 3 round duration, 1 or 2 minutes for round duration. Then go and kill your second controller, rinse and repeat.
Those who wish to vote negative, at least please give the courtesy of explaining why you voted it down. I simply explained my method of what worked for me to get the achievement.