This achievement is awarded for being a member of the winning team in any mode in multiplayer.
You need not be the best player. If you are stun boosting level 20, this will come naturally as your team will do better on several occasions.
If you just want to pop this, play some team modes where there are few teams (such as Manhunt - 2 teams). Eventually you will be on the better team.
This will pop at match end. Good luck!