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