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