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