How to Obtain: Earn 48 stars in Special Ops Mission Mode.
There are a total of 16 Mission maps you'll need to play here. To make it a little easier, these are best done with one other player. You may also want to note, that not all of the maps are available from the start. Some require you to be a certain level within the Missions mode. By simply playing the other maps, you should have no trouble reaching these ranks.
The Missions mode is split into 3 difficulties and each one offers their own * rank. The higher you go the more *'s you'll get upon completion. So to gain this achievement, you'll need to play and complete all 16 Missions on the Veteran difficulty.
Regular = * Hardened = ** Veteran = ***
Tier 1: Level 0
■Hit and Run
Tier 2: Level 5
Tier 3: Level 10
Tier 4: Level 15
■Flood the Market