Return of the Obra Dinn

To achieve this you will need to claim that 57 souls were killed by the Captain, and that the Captain died via suicide. Then when you exit the boat you should get the achievement.

You will most likely need to start a new save, and unlock all the memories which takes roughly 2 hours. Make sure to not identify any fates correctly if the death wasn't by the Captain otherwise you will be locked out and need to start a new save. No names need to be identified, and the death can be anything caused by the Captain (ie axed, drowned.)