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