Here is the full list of all 46 Army of TWO: The Devil's Cartel achievements worth 1,000 gamerscore.
Complete New Blood
Perform 10 cover to cover transition in a row
Make your first kill as a rookie (in Cause and Effect mission)
Complete Cause and Effect
Kill 3 targets or more using an explosive object in any level
Perform a melee kill while you're in Overkill
Complete Rally Point
Complete Outside Contact
Level up to Rank 5
Fully customize a weapon with 6 customizable parts or more
Perform 50 Hat Shots
Complete Last Resort
Perform 100 Headshots
Perform a x10 Co-op Combo
Create your own Custom Mask
Complete Salvation
Destroyed 500 objects
Kill 3 targets with 1 grenade
Headshot a target while blind firing
Complete Enemy Territory
Complete Narco Hell
Level up to Rank 15
100 targets killed using either an MMG or an MGL
Perform 250 Flank, Surprise and/or Tag Team kills
Kill 10 Brutes in Physical Confrontation
Complete Assault
Complete Confrontation
Complete the Campaign
500 targets killed while in cover
Apply the maximum number of layers on a customized mask
200 targets killed in single Overkill (Triggered by you)
200 targets killed in single Overkill (Triggered by your partner)
You took the Aggro for 100 Flank kills
Perform 100 melee kills
You didn’t go wounded once in a mission (medium, hard or insane)
Destroy 50 cars
Players simultaneously killed 2 unaware targets
Level up to Rank 25
Buy All Guns
Complete the game on Insane
Perform 50 Backstabs
Buy All Outfits
Buy all Weapons, Tattoos, Masks and Outfits
200 targets killed in double Overkill
Perform 10 melee kills on wounded targets
Complete a mission (excluding New Blood) with a human partner