Here is the full list of all 101 In Death achievements.
Slaughter 73 Monks
Slay 16 Temple Knights
Make a Headshot from a mile away
Buy an item from a Reliquary
Deal 10,000 damage in one afterlife
Exterminate 71 Abominations
Slaughter 23 Monks
Slay 3 Temple Knights
Kill 101 enemies with Combat arrows
Die
Exterminate 21 Abominations
Make a Headshot from far away
Kill 9 enemies within a short time period
Deal 100,000 damage in one afterlife
Deal 1,000,000 damage in one afterlife
Score 26 headshots in one afterlife
Score 56 headshots in one afterlife
Score 126 headshots in one afterlife
Score 266 headshots in one afterlife
Score 666 headshots in one afterlife
Loot 6,000 gold pieces in one afterlife
Loot 12,000 gold pieces in one afterlife
Loot 24,000 gold pieces in one afterlife
Kill 15 enemies within a short time period
Kill 21 enemies within a short time period
Exterminate 251 Abominations
Exterminate 851 Abominations
Exterminate 3001 Abominations
Slaughter 233 Monks
Slaughter 833 Monks
Slaughter 3033 Monks
Slay 80 Temple Knights
Slay 540 Temple Knights
Slay 2190 Temple Knights
Banish 21 Ghosts
Banish 61 Ghosts
Banish 181 Ghosts
Banish 561 Ghosts
Banish 1701 Ghosts
Kill 9 Incubi
Kill 39 Incubi
Kill 149 Incubi
Execute 9 Banshees
Execute 29 Banshees
Execute 69 Banshees
Execute 159 Banshees
Execute 409 Banshees
Murder 16 Cupids
Murder 66 Cupids
Murder 266 Cupids
Murder 966 Cupids
Murder 3666 Cupids
Bring salvation to 3 Orphans
Bring salvation to 23 Orphans
Bring salvation to 103 Orphans
Challenge another player
Make the most unbelievably long Headshot
Succesfully respond and win a challenge from another player
Kill a large number of enemies with a single Curse
Kill a large number of enemies with a single Tempest
Kill 666 enemies who haven't noticed your presence
Kill a frozen enemy with fire
Knock a Cupid out of the sky using your shield
Save 3 Orphans in one afterlife
Save 5 Orphans in one afterlife
Save 7 Orphans in one afterlife
Kill 266 Burning enemies
Kill 266 Cursed enemies
Kill 266 Frozen enemies
Kill 666 Poisoned enemies
Kill 101 enemies with Wrath of God
Kill 666 enemies with Azure Fury
Kill 666 enemies with Cataclysm
Kill 666 enemies with Barrage of Needles
Kill 101 enemies with Incursion
Kill 666 with Tempest
Kill 666 enemies with Ball of Lightning
Reduce Anakim The Abominable to 70% Health
Emerge back from Pit of Immolation
Emerge back from Pit of Perdition
Emerge back from Pit of Reformation
Defeat Anakim The Abominable
Defeat Gabriel The Fallen
Complete Purgatory without spending gold
Defeat Anakim The Abominable at full health
Reduce Gabriel The Fallen to 50% health
Complete Paradise Lost without spending gold
Defeat Gabriel The Fallen at full health
Complete Pit of Immolation at full health
Complete Pit of Perdition at full health
Complete Pit of Reformation at full health
Complete Purgatory in 38 minutes
Complete Purgatory in 32 minutes
Complete Purgatory in 26 minutes
Complete Pit of Immolation in 7 minutes
Complete Pit of Perdition in 8 minutes
Complete Pit of Reformation in 9 minutes
Complete Paradise Lost in 33 minutes
Complete Paradise Lost in 27 minutes
Complete Paradise Lost in 21 minutes
Complete Paradise Lost using the crossbow