Here is the full list of all 35 Postal III achievements.
Complete game using only melee.
Complete game using only the pistol.
Beat game with zero kills.n(zombies and bosses don't count)
Kill no animals in one playthrough.
Complete Good path without falling off.
Complete game killing only males.
Kill/incapacitate 235 terrorists.
Respawn 20 times.
Kill 1000 unarmed bystanders.
Spend 900 seconds or more in catnip bullet time.
Finish your business with Krotchy.
Escape from prison.
Destroy 50 cars.
Smash 50 windows.
Piss 100 gallons of urine.
Suck up 500 items with the shop vac.
200 kills using M-60.
300 headshot/decap kills.
50 kills using bees.
150 kills using fire.
Euthanise 30 elderly folks.
50 kills using cat.
50 badgersaw kills.
50 kills using boomerang machete.
100 kills using machete in melee.
Make Venezuela peacemakers go home.
Beat the game once. No restrictions apply. Everyone's a winner.
Take out all the criminal scum infesting Catharsis!
Return Thegways to the owner
Arrest eco zealots leader.
Taze 200 victims.
Arrest 200 perps.
Choose path for the first time.
Disobey orders, given to you, and see what happens.
Injure yourself.