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