The Achievement "field medic" has you heal your partner 25 times. In the part of the Miami level when you have to find the breaker for the monorail (the part when you are on the hovercraft), there are wires in the water that lead you to the breaker needed to turn on the monorail, have a friend walk into the wires, the electricity will automatically shut off and you can heal them. Keep on turning the power on while the other player stands on the wires and you will have the Achievement in no time.
Easy Two Eyes Achievement
Near the start of the level, you need to disable jets that are on the runway of the carrier. When you get to the first set of jets, a helicopter will come to the right of you, activate co-op snipe mode, and shoot the people while they are still in the helicopter, this is very convenient because there are about 5 people in the helicopter. After that, you should get the "Two Eyes are Better Than One" Achievement.
The Six Secret Achievements
You get the 6 secret achievements by doing co-op campaign. 1st and 2nd level are worth 30 points and the other 4 are worth 15 each.
Secret Achievement 1. (30)
Complete Mission 1 (Somalia) On The Difficulty Of Contractor Of Higher.
Secret Achievement 2. (30)
Complete Mission 2 (Afghanistan) On The Difficulty Of Contractor Of Higher.
Secret Achievement 3. (15)
Complete Mission 3 (Iraq) On The Difficulty Of Contractor Of Higher.
Secret Achievement 4. (15)
Complete Mission 4 (Aircraft Carrier)On The Difficulty Of Contractor Of Higher.
Secret Achievement 5. (15)
Complete Mission 5 (China) On The Difficulty Of Contractor Of Higher.
Secret Achievement 6. (15)
Complete Mission 6 (Miami) On The Difficulty Of Contractor Of Higher.
Two Super Achievements
Okay, so I've been wondering why people are having such a problem getting the Fear is the Mind Killer and the Field Medic achievements. So this should make it very simple. While in the training session you'll be behind a block shooting at the guy in the turret. Just don't stop shooting at him. After 1 minute, you'll have the Fear is the Mind Killer achievement. Then get you and your partner alone. All you have to do for the Field Medic achievement, is to shoot him down and revive him 25 times. I've tried both and they're very easy to do.
True SSC Challenger (25) - Win every stage of a ranked three round SSC Challenge match.
Get All Primary Weapons
All Primary Weapons
Beat the game on the Recruit difficulty.
All Secondary Weapons
Beat the game on Professional.
All Special Weapons
Beat the game on Professional.
Beat the game once on Recruit or Contractor.
Alright, Who Wants Some? (20) - Kill 250 enemies total using SMGs.
Beast with Two Fronts (20) - Kill 50 enemies total in Back-to-Back.
Big Boom! Big Bada Boom! (20) - Kill 25 enemies total using RPGs.
Boots on the Ground (10) - Finish playing a versus ranked match.
Dead Man's Hand (20) - Kill 150 enemies total using Handguns.
Elite PMC (50) - Complete all missions as a Professional.
Fear is The Mind Killer (45) - Spend 1 minute straight at full Aggro.
Field Medic (30) - Drag and heal your partner 25 times.
Fission Mailed (20) - Kill 25 Martyrs by shooting the Bomb Packs on their chests.
Flip You. Flip You For Real (20) - Kill 50 enemies total using the Melee Attack.
If I Were a Rich Man (40) - Earn one million dollars in total over the course of campaign mode.
If It Bleeds, We Can Kill It (30) - Kill 25 Heavy Armor enemies.
L'Abattoir (30) - Kill 100 enemies while in the power mode of Overkill.
Man of Many Masks (50) - Purchase every mask variant.
My Kind of Case! (40) - Collect all of the information cases in the entire game.
My Virtual Friend (35) - Complete all missions with the Partner AI.
One Gun is Enough (35) - Win a ranked match without purchasing any additional weapons.
One Shot. One Kill. (20) - Kill 100 enemies total using Sniper Rifles.
Out of Debt (15) - Heal your partner for the first time. Training does not count.
Retirement Savings Plan (40) - Earn one billion dollars in total in ranked matches.
Running Man (30) - Kill 75 enemies while in the stealth mode of Overkill.
Say Hello to my Little Friends (45) - Purchase the MP7, M134, DAO-X Protecta, MGL MK-X, and the M107 Light Fifty.
Seven-six-two Millimeter (20) - Kill 250 enemies total using Assault Rifles.
Spray and Pray (20) - Kill 250 enemies total using Machine Guns.
Starting a Riot (30) - Kill 50 enemies total in Co-op Riot Shield.
Stonewall (30) - Kill 30 enemies using the Riot Shield melee attack
Surviving The Game (25) - Complete a ranked match without ever needing to be revived.
The Devil's in the Details (20) - Complete 20 minor objectives in a ranked match.
This is my Boom Stick! (20) - Kill 250 enemies total using Shotguns.
Two Eyes are Better Than One (35) - Kill 5 enemies total using Co-op Snipe.
Weapon Specialist (15) - Purchase 3 weapons.
Killing Armoured Gunners Without Stealth
If you encounter an armored opponent, the Aggro Training tells you that one person holds the position, while the other tries their best not to get seen by the opponent to shoot them from behind. Now, the easy and fast way to do it is to shoot him with any gun, in the head. Soon, he will either die, or fall to the floor, not injured, but defenseless. That is when you shoot at him wherever. WARNING!!! This process is to be done as quickly as possible, or he will get up and shoot at you if you are close enough. So basically, your strongest weapon against the armored opponents, can be the worst weapons.