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