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