Here is the full list of all 21 Envy the Dead achievements.
Complete stage 1
Defeat zombies in battle
Defeat survivors in battle
Equip character with any armor
Explode barrel or propane
Use conviction answer
Gather any supply on x8 rate
Feed dying hungry character
Heal dying injured character
Train character to level 4
Craft turret
Kill butcher boss
Kill stinker boss
Complete stage 2
Complete game
Complete stage 1 on hardcore
Complete stage 2 on hardcore
Complete game on hardcore
Survive wave 10 in survival
Survive wave 20 in survival
Survive wave 30 in survival