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