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