Here is the full list of all 69 The Unliving achievements.
Defeat the second boss
Defeat the first boss
Kill 100 enemies with a basic or scythe attack
Use an echo for a spell or rune
Lose a health vial without dying
Kill 25 enemies with a basic or scythe attack
Use bone for a spell or rune
Use blood for a spell or rune
Consume health when casting
Resurrect an undead
Kill an enemy with a basic or scythe attack
Kill 500 enemies with a basic or scythe attack
Resurrect 100 undead
Resurrect 1,000 undead