Here is the full list of all 53 Beyond the Long Night achievements.
Beat a run in the explorer hat
Reach the Sanctuary
Meet Tetchy and Dopey
Reach Hope's Peak
Meet Archie
Reach the Forbidden Temple
Meet Bobbins
Discover the Storm
Meet the Annoying Child
Meet Eebi
Meet the Pilgrim
Meet Pickles
Return to the Dark Mountain after your first death.
Speak to Pickles after returning from the Overworld
Meet Umpa
Discover the Ear Horn
Discover the invisible gate in the Sanctuary
Return to the farm after the cows escape
Engrave a cow statue
Engrave all of the cow statues
Open all of the Annoying Child's shops
Give the Annoying Child enough shiny stones to make a golden bust of themselves
Get the annoying child to recognise you after you return from the Overworld
Find the Annoying Child awake in the Strange Dimension
Escort Tetchy and Dopey to the Sanctuary
Find Tetchy's remains after they escape to the Overworld
Find the Pilgrim after they leave the altar room
Learn everything you can from Archie
Find the remains of Archie after they escape to the Overworld
Find Archie after they fail to escape to the Overworld
Meet Sara
Choose every type of stone at the monuments
Discover all three runes in the monuments
Reach the strange dimension
Discover the secret combination within the strange dimension
Defeat Sara
Escape the Long Night
Find one of the old diary entries
Discover all of the old diary entries
Discover every Upgrade and Superpower in the game
Beat an encore run in the explorer hat
Beat a run in the party hat
Beat an encore run in the party hat
Beat a run in the mushroom hat
Beat an encore run in the mushroom hat
Beat a run in the iron hat
Beat an encore run in the iron hat
Beat a run in under 25 minutes
Beat a run in under 25 minutes without taking any damage
Beat a run without using your Superpower
Beat a run without collecting any upgrades
Beat a run using your main bullets weapon 100 times or less
Beat a run having visited every room on the map