You took the Aggro for 100 Flank kills

Perform a x10 Co-op Combo

Perform 250 Flank, Surprise and/or Tag Team kills

Perform 100 melee kills

Perform a melee kill while you're in Overkill

Bring a veteran officer aboard.

Visit a store in the single-player campaign.

Kill 3 targets with 1 grenade

Fully customize a weapon with 6 customizable parts or more

Destroy 50 cars

Level up to Rank 5

Complete a mission (excluding New Blood) with a human partner

Return to active duty.