I found out that you can actually start up solo lobbies and do acheivements that do not require kills due to you being completely alone.
At main menu click "Create a Game" then choose the map you desire, so for this achievement it is "Fishtank Frenzy".
Then down the bottom of your screen, Tick the "invite Only" button and press "P2P" this will take you to a lobby and you can just press "Force Start Timer" and away you go :)
This achievement is relatively easy. Just go from one side of the map, pick up the enemy flag and run back to your own flag with it :)