Here is the full list of all 43 Over 9000 Zombies! achievements.
Kill 90,000+ Zombies!
Voted the greatest zombie of all time!
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!
Kill over 1000 zombie eyes!
If only he had the body of a horse...
A jail is an isolated system.
The army of the undead will march at daybreak!
No 8th symphony for zombie Sibelius!
Derail the Waltz of the Undead!
Kill over 1000 crabs!
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!
Get 30 kills per second!
Get 15,000 damage per second!
Collect 100 Power Ups!
Kill over 1000 zombie dogs!
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!
Construct a turret from scrap metal!
Zombie Napoleon meets his zombie Waterloo!
You watched the world burn, and survived. It was kind of cool.
Green IS good.
Kill 1000+ Zombies!
You won that race.
Get 5,000 damage per second!
Making some progress...
The first day is always the hardest, except in this case, it's the easiest.
Get 10 kills per second!
Kill 900,000+ Zombies!
Construct 100 automated turrets.
Construct 1000 Turrets from random scraps of metal!
Participate in a multiplayer game.