This achievement can be done in player matches, with two people who have a guest. Simply take it in turns, using the method described in the Again, and Again, and AGAIN..., but instead of "VIP" set the mode to "Battle", and make sure you both sign in a guest or second profile. Simply have both guests and one of the players kill themselves at the beginning of each match. Set it for one-round matches.
Alternate method, by III L3giOn III:
If you are boosting with a friend, play 2 on 2 "Team VIP" on any map, in a private match. Both you and your friend will need to have a second controller connected for a 3rd and 4th player.
Have you and your friend on the same team, and your guest and your friend's guest on the other team. As soon as the match starts, have the Guest VIP blow himself up. Repeat 24 times.