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!
The army of the undead will march at daybreak!
Get 30 kills per second!
Construct 100 automated turrets.
Zombie Napoleon meets his zombie Waterloo!
Voted the greatest zombie of all time!
Derail the Waltz of the Undead!
Kill over 1000 zombie eyes!
Collect 100 Power Ups!
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!
Kill 9,000+ Zombies!
Kill over 1000 zombie dogs!
Terror possessed me then!
If only he had the body of a horse...
A jail is an isolated system.
Kill over 1000 crabs!
Participate in a multiplayer game.
Blood and Flesh can be trusted.
Decreased Zombotropy.
Get 15,000 damage per second!
Quoth the Raven "Nevermore."
Kill over 1000 zombie crows!
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...
No 8th symphony for zombie Sibelius!
Not a wimp.
Kill 1000+ Zombies!
Lots of progress!
You watched the world burn, and survived. It was kind of cool.
Construct a turret from scrap metal!
Green IS good.
You won that race.
Making some progress...
Get 5,000 damage per second!
Get 10 kills per second!
The first day is always the hardest, except in this case, it's the easiest.