The list of Postal 3 Achievements can be viewed below, there are 38 achievements in the game and each has it's own requirements as you progress during the game. If you need additinal help with the achievements then take a look at the postal 3 walkthrough.
Postal 3 Achievements List
EMO
Injure yourself.
SPECIAL OLYMPIAN
Beat the game once. No restrictions apply. Everyone's a winner.
NEUROSURGEON
300 headshot/decap kills.
SCHWARZENEGGER
200 kills using M-60.
DO NOT PUSH THE BUTTON!
Disobey orders, given to you, and see what happens.
DANNY TREJO
100 kills using machete in melee.
COMMIES GO HOME!
Make Venezuela peacemakers go home.
DON'T TAZE ME BRO
Taze 200 victims.
SUCKTASTIC!
Suck up 500 items with the shop vac.
WOLVERINES R GHEY
50 badgersaw kills.
PROPERTY DAMAGE
Smash 50 windows.
PSYCHO DUNDEE
50 kills using boomerang machete.
T.J. HOOKER
Arrest 200 perps.
PRODUCT RECALL
Destroy 50 cars.
REPO MAN
Return Thegways to the owner
CAT WRANGLER
50 kills using cat.
CAMELBACK
Piss 100 gallons of urine.
SCOFIELD
Escape from prison.
JACK THOMPSON WAS RIGHT
Kill 1000 unarmed bystanders.
THERE IS NO SPOON
Spend 900 seconds or more in catnip bullet time.
AIN'T GOT COJONES!
Finish your business with Krotchy.
FAIL ZOMBIE
Respawn 20 times.
DADDY NEVER LOVED ME
Complete game killing only males.
ARSONIST
150 kills using fire.
ENTOMOLOGIST
50 kills using bees.
I AM THE LAW
Complete Good path without falling off.
PETA CHAIRMAN
Kill no animals in one playthrough.
ALL PERPS MUST DIE!
Take out all the criminal scum infesting Catharsis!
THE CHOICE WAS YOURS!
Choose path for the first time.
SAYANARA, TREE HUGGERS
Arrest eco zealots leader.
EASTWOOD
Complete game using only the pistol.
REAL AMERICAN
Kill/incapacitate 235 terrorists.
MEGA-SADIST
200 injured or death-crawling victims NOT finished off.
PERSONAL JESUS
Beat game with zero kills.n(zombies and bosses don't count)
BIPOLAR
Swap paths 5 times in one playthrough.
CHAMP WHISPERER
50 kills using dog.
STALLONE
Complete game using only melee.
KAVORKIAN
Euthanise 30 elderly folks.