Gears of War: Judgment

Simple enough, just start up a campaign on normal difficulty and earn all 3 stars on 25 segments. Even if you don't get 3 stars on every segment don't worry, there's more than 25 segments, so you shouldn't have any difficulty getting enough stars.

To get the three stars, you'll need to complete the declassified challenges, kill as many Locust as possible and get executions.