Here is the full list of all 41 OMORI achievements worth 1,000 gamerscore. It takes around 60-80 hours to unlock all of the achievements on Xbox One.
Unlock all badges. Thank you for playing OMORI.
Defeat DOWNLOAD WINDOW.
Recover at all of MARI's picnics.
Defeat 100 BUNNIES.
Defeat MR. JAWSUM.
Reach the bad ending.
Complete the FOE FACTS! journal.
Have a ghost party.
Defeat THE EARTH.
Wake up in the morning.
Defeat ???.
Defeat MUTANTHEART.
Get the FLOWER CROWN from BASIL.
Defeat PERFECTHEART.
Insert every song into GINO'S JUKEBOX.
Lose to KIM and VANCE.
Defeat SWEETHEART.
Reach the good ending.
Go to sleep after a long day.
Commission all of ROCOCO's art.
Defeat KITE KID.
Get all rewards from the RECYCLING MACHINE.
Defeat every SOMETHING at the bottom of the LOST LIBRARY.
Defeat SPACE EX-BOYFRIEND.
Defeat SPACE EX-HUSBAND.
Defeat SLIME GIRLS.
Commission ROCOCO.
Reach the other ending.
Defeat the HOOLIGANS with PEPPER SPRAY.
Defeat PLUTO and THE EARTH.
Defeat ROBOHEART.
Defeat the PET ROCK champion.
Look through all telescopes.
Feed the STRAY CAT every day and sunset.
Defeat UNBREAD TWINS.
Receive all FLOWERS in the hospital.
Take the KEEPER OF THE CASTLE's power.
Visit all mirrors.
Defeat HUMPHREY.
Defeat PLUTO (EXPANDED).
Give FLOWERS to MARI.