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