Here is the full list of all 16 Defend Your Crypt achievements.
Kill 250 thieves.
Kill 150 thieves.
Kill 100 thieves.
Complete one level with only 1 gold unit left.
Make 1 thief sad.
Watch two thieves doing a High Five!
Kill 10 thieves.
Complete one level without speed up.
Complete one level without losing any gold.
Finish all levels.
Kill 3 thieves with the water trap at the same time.
Kill 200 thieves with a crusher trap.
Burn 30 thieves.
Kill 500 thieves.
Kill 1.000 thieves.
Kill 2.000 thieves.