Here is the full list of all 39 Paradise Killer achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Collect all Island Sequence Mementos
Collect every shrine tablet
Speak to every Shinji
Find all recordings
Collect all drinks
Unlock all footbath upgrades
Complete the Syndicate HQ puzzle
Give a treat to [REDACTED]
Return the missing gem
Deliver the manifesto letter
Deliver reassurance that justice was done (it wasn’t)
Tell the ghost who they are
Acquire the Cosmos Starlight upgrade
Acquire the Pyramid Starlight upgrade
Acquire the Worship Starlight upgrade
Acquire Elusive Chocolate
Unload the cargo
Speak to a [REDACTED]
Access the Syndicate Graveyard
Access the barracks
Visit [REDACTED]
Use the [REDACTED] to open the [REDACTED]
Achieve max hangout level with Carmelina
Activate all Crying Grudge statues
Complete the valve puzzle
Find all music tracks
Tell the ghost what happened to their friend
Achieve max hangout level with Akiko
Achieve max hangout level with Crimson
Achieve max hangout level with Doom Jazz
Achieve max hangout level with Henry
Achieve max hangout level with Lydia
Achieve max hangout level with Sam
Achieve max hangout level with Witness
Achieve max hangout level with Yuri
Achieve max hangout level with One Last Kiss
Speedrun the game and complete it in under 10 minutes
Collect all Starlight Skins
Collected all bottles of whisky