Here is the full list of all 51 Door Kickers: Action Squad achievements worth 1,000 gamerscore.
Use 5 extra lives in the same mission
Successfully complete all missions in Chapter 5
3-Star all missions in Chapter 5
3-Star all missions in Chapter 4
Successfully complete all missions in Chapter 4
3-Star all missions in Chapter 3
Successfully complete all missions in Chapter 3
Rescue 1000 hostages
Rescue 50 Wounded Policemen
Blow Open 100 Doors
Make 5 VIP Arrests
3-Star all missions in Chapter 2
Successfully complete all missions in Chapter 2
Unlock Chapter 6
Kick Open 1000 Doors
Kill 50 Hostages
Stun 500 enemies
Unlock Chapter 5
Get 100 kills as Shield
Get 100 kills as Agent Fergie
Kill yourself with your own explosives
Unlock Chapter 4
Complete a level without taking any damage whatsoever
3-Star all missions in Chapter 1
Successfully complete all missions in Chapter 1
Set 20 enemies on fire
Kill an enemy with an elevator
Unlock Chapter 3
Kill 50 rats
Kill 3 enemies with one breaching charge
Use sniper support to kill 100 enemies
Kill 1000 bad guys
Get 100 kills as Breacher
Get 100 kills as Recon
Unlock Chapter 2
Get 100 kills as Assaulter
Get 100 kills as Off-duty Guy
Rescue 50 hostages
Kick Open 100 Doors
Collect your first secret item
Kill 50 bad guys
Get 3 stars in a mission
Kill 3 enemies by blowing up one barrel
Win one mission in Coop
Disarm 30 bombs
Use sniper support to kill 1000 enemies
Resurrect another player 5 times in the same mission
Collect all 20 secret items
Defuse a bomb in the last 3 seconds
Complete all missions in chapter 6
3-Star all missions in Chapter 7