This achievement is called I Don't Want To Go! and requires you to Defeat the Reaper!
Now that the obvious has been stated, let's get on with it.
There is only one way that I know to defeat the Reaper, and it's to throw him out a window.
I'm sure there are a lot of occurrences where you can do this, but I personaly did it in Chapter 2, Scene 25 : Lower Corridors.
In this scene you have to battle haunted chairs and the rule is to not take any damage. Of course to summon the reaper we do want to take damage.
When summoned, avoid his finger which will one shot you. You can knock him down when he is using his scythe as a guitar, or by throwing an item at him, say one flower pot at the entrance of the room
When he is knocked down, now is your chance to not let him get on his feet and kick him towards the window. When he is finally out, the deathly white glow that surrounds him will disappear and a few seconds later the achievement will pop!
And there he did go!