Image: UbisoftOfficial screenshot from Ubisoft.
A well-kept secret is the story achievement of the Jack the Ripper DLC: you get it for finishing its main memories as Evie in 1888.
Complete Sequence 10, A Monster's Creed, from start to finish.
The achievement's own text says the Ripper dies and his identity stays secret, which is why the DLC's ending is in our spoiler sections.