Here is the full list of all 43 Over 9000 Zombies! achievements.
Kill 90,000+ Zombies!
Kill 900,000+ Zombies!
Construct 100 automated turrets.
Construct 1000 Turrets from random scraps of metal!
Collect 100 Power Ups!
Participate in a multiplayer game.
Derail the Waltz of the Undead!
The army of the undead will march at daybreak!
Kill over 1000 crabs!
The zombie world is independent of our will.
Kill over 1000 zombie eyes!
Abused patience turns to fury!
Health is the greatest gift, a close second is BRAINS!
Terror possessed me then!
If only he had the body of a horse...
No 8th symphony for zombie Sibelius!
A jail is an isolated system.
Get 30 kills per second!
Blood and Flesh can be trusted.
Vote for Zombie Thomas Jefferson, or don't.
Kill over 1000 zombie dogs!
Kill 9,000+ Zombies!
Decreased Zombotropy.
Quoth the Raven "Nevermore."
Kill over 1000 zombie crows!
Zombie Napoleon meets his zombie Waterloo!
Don't call me slow!
Get 15,000 damage per second!
Your world didn't end!
Voted the greatest zombie of all time!
You didn't donate your organs...
It didn't taste like chocolate ice cream either...
Not a wimp.
Lots of progress!
You watched the world burn, and survived. It was kind of cool.
Green IS good.
Kill 1000+ Zombies!
You won that race.
Get 10 kills per second!
Get 5,000 damage per second!
Making some progress...
Construct a turret from scrap metal!
The first day is always the hardest, except in this case, it's the easiest.