Bronze:

Not What I Thought It Was
Objective: Complete Chapter 1 on any difficulty level

A Steep Descent
Objective: Complete Chapter 2 on any difficulty level

A Decent Animal
Objective: Complete Chapter 3 on any difficulty level

Emergency Room
Objective: Complete Chapter 4 on any difficulty level

Gone Shopping
Objective: Complete Chapter 5 on any difficulty level

Meat Bag
Objective: Use 15 enemies as human shields

Chaaaaarge!
Objective: Charge through 20 enemies

Grenadier
Objective: Kill 3 or more enemies with a single grenade

Pistolier
Objective: Kill 150 enemies with pistols

Old Faithful
Objective: Kill 400 enemies with assault rifles, submachine guns or shutguns

One Shot, One Kill
Objective: Kill 100 enemies with a sniper rifle

Quick Draw
Objective: Kill 25 enemies with a quickdraw from mock surrender

Open Hand Slap!
Objective: Kill 50 enemies with a melee or bayonet

Not So Bad After All
Objective: Tie up 15 enemy combatants instead of executing them

Healer
Objective: Heal your partner 10 times

Co-Op Sniper
Objective: Co-op snipe 5 enemies

Attention Grabber
Objective: Allow your partner to snipe 5 guys while in mock surrender

In Synch
Objective: Kill two enemies with simultaneous quick draws while in co-op mock surrender

Pumpkin Patch
Objective: Shoot 2 enemies in the head with a single bullet

Total Fist Bump Destruction
Objective: Finish the game as best friends

Total Fist Bump Deflation
Objective: Finish the game in a fractured friendship

The Truth Is Right Here
Objective: Listen to all of the radio broadcasts

Loot and Pillage
Objective: Collect $1,000,000

Hate Monger
Objective: Customize a primary weapon to high aggro

The Optimist
Objective: Make a positive coop morality choice

The Pessimist
Objective: Make a negative coop choice

Fresh Meat
Objective: Versus: Revive your partner and perform a partner reload during the same public match

Fancy Meeting You Here
Objective: Versus: Invite a friend before joining a lobby to play a public match

Big Game Hunting
Objective: Versus: Kill both members of a single partnership during a public match

Job Seeker
Objective: Versus: In public matches, kill a player with either the primary or secondary weapon from every weapon kit

DIY PMC
Objective: Versus: Create a custom facemask online (www.armyoftwo.com) and wear it in a public match

Death Dealer
Objective: Versus: Kill 10 players...