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