Unless there is a workaround to get this to pop - pretty much out of luck unless you can gather I think 32 players (at the very least) to queue Fireteam and then eliminate enemy squads to get a Squad Wipe medal.
Other than that its pretty much impossible because of the amount of players you need to start and the fact the games old now and everyone queues Nuketown and Quickplay :/
- Additional note - if you already have this achievement on say Xbox/PS then you would only need to get 1 squad wipe (this applies to all the other multiplayer achievements - if you have 50 wins and no achievement, getting 1 win will give the achievement)