Here is the full list of all 149 Nightmare Reaper achievements.
Reach New game+ 1
Find everything in the hospital
Complete buried ruins
Get the sacrifice ending
Kick a boss
Complete blood and brimstone
Complete the flesh pits
Unlock 8 arenas
Complete sorcerer's mansion
Complete the empty
Buy all skills from world 5
Buy 100 skills from the tree
Complete crushing depths
Obtain 1000000 jade
Obtain 20 Vs
Complete the wasteland
Obtain 20 horse waters
Complete moon terror
Complete fields of death
Complete 45 levels with pills
Buy 50 jade upgrades
Complete gibbs medical center
Complete 75 random events
Obtain 20 reflections
Complete void beneath
Sell 500 weapons
Unlock 5 arenas
Complete boulder penitentiary
Burn freeze and shock an enemy
Complete rust works
Kill 5000 enemies
Complete murky docks
Complete vermilion princess
Buy 75 skills from the tree
Complete tower of toil
Complete gardens of woe
Obtain 20 nightmare reapers
Obtain 240000 jade
Complete a level with 20 toxicity
Buy all skills from world 4
Complete carnage way
Buy all skills from world 3
Obtain 1000 headshot kills
Complete 15 levels with pills
complete the descent
Obtain 1000000 gold
Buy all skills from world 2
Buy 50 skills from the tree
Buy all skills from world 1
Buy 10 jade upgrades
Reach round 10 in an arena
Break 2500 clutter objects
Complete gloom mansion
Obtain 5 Vs
Unlock 2 arenas
Kick 50 enemies to death
Complete putrid sewers
Complete drudge village
Obtain 60000 jade
Buy 25 skills from the tree
Complete 5 levels with pills
Accept 5 merchant offers
Complete disavowed town
Obtain 1000 treasures
Obtain 5 horse waters
Kill 3 enemies with one bullet
Obtain 20000 jade
Complete sulfuric mines
Get all bonuses in a level
Get all treasures in a level
Complete forsaken village
Complete 15 random events
Obtain 5 nightmare reapers
Complete immemorial woods
Obtain 5 reflections
Obtain 150000 gold
Kill 500 enemies
Obtain a level 3 weapon
Buy 10 skills from the tree
Break 250 clutter objects
Complete spore pit
Wake up prematurely
Pickup a weapon after death
Obtain horse water
Sell 50 weapons
Obtain a legendary weapon
Sell 25 weapons
Get all secrets in a level
Break 100 clutter objects
Obtain V
Complete hollow stone
Obtain 100 headshot kills
Obtain 50000 gold
Reach bynnyhop max speed
Sell 10 weapons
get all kills in a level
Buy a skill from the tree
Obtain nightmare reaper
Obtain 100 treasures
Complete 5 random events
Kill 100 enemies
Obtain a 35x combo
Obtain a 25x combo
Obtain a 15x combo
Obtain a rare weapon
Obtain a 5x combo
Obtain reflection
Obtain 20 headshot kills
Obtain an uncommon weapon
Obtain 10000 gold
Obtain 20 treasures
Kill 30 enemies
Obtain a level 2 weapon
Do 20 rocket jumps
50 high falls into water
Douse yourself 50 times
Buy 125 skills from the tree
Buy all skills from world 6
Buy all skills from world 7
Buy all skills from world 8
Obtain 10000 treasures
Break 10000 clutter objects
Obtain 500 Vs
Obtain 500 horse waters
Obtain 500 reflections
Obtain 500 nightmare reapers
Obtain 10000 headshot kills
Complete 250 random events
Complete 135 levels with pills
Complete 405 levels with pills
Get the control ending
Sell a weapon for 1000000
Have a carried barrel explode
Start a level with no weapon
Lose 2000 life as blood ammo
Change a stat to +2 attack
Change a stat to blood ammo
Complete a level with 100 toxicity
Complete a level with 250 toxicity
Buy 100 jade upgrades
Buy 180 jade upgrades
Reach round 50 in an arena
Reach round 100 in an arena
Have a pet with 2 skills
Have 2 pets
Unlock all pets
Unlock all pet skills
Reach New game+ 2
Reach New game+ 3