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