Story related but potentially missable.
The ending you get is based on your karma levels* and this trophy pops AFTER you've beaten the end boss, whichever one it is, so there's unfortunately no logical way to reload an old save to pick an alternate route to save you from doing multiple runs.
The only ending you need to worry about is on the Truthful route as that will overwrite the other three and thus void the chance to get them.
Moral karma is always on the LEFT of the options when you're given a choice. This route is based on heroic acts and making the "tough choices" for the group.
As long as your karma is leaning towards the red end of the spectrum you should be able to get this one.
*at the end of chapter 8 you'll be given options on what to do based on your karma levels. Any karma over (for arguments sake) 35 will appear and anything under that number will not and essentially "lock you out" of an ending.