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