Here is the full list of all 43 In Stars And Time achievements.
Finish getting ready.
Die for the first time.
Die against the King.
Beat the King.
Get to the end.
Hang out with Mirabelle.
Hang out with Odile.
Hang out with Bonnie.
Hang out with Isabeau.
Hang out with everyone, and get to the end.
Hang out with everyone, and get to the end, thrice.
Talk to the King.
Learn more about the loops.
Save Vaugarde.
Talk to a statue.
Wait for it.
Have a talk.
Act suspicious.
Something about teaching…
Something about a shoulder…
Something about a joke...
Something about snacks…
Something about spicy food…
See a ghost.
See three ghosts in a single loop.
Do a Jackpot Attack for the first time.
Loop 20 times.
Loop 50 times.
Loop 100 times.
Find out about The Incident.
Think about your dagger.
Get everyone to their max level in the same loop.
Get every weapon in the same loop.
Get every accessory.
Get every memory.
Snack on some pineapple slices.
Die every way possible.
Get to the end 5 times.
Show Loop a souvenir.
Show Loop a specific souvenir, at a specific time.
Get every chat with Loop.
Have one last chat with Loop.