Caveat: written with accordance to Roman Catholic view of things as that's the one I know anything relevant. By the way, I don't disagree with you, but rd95's post feels compelling to drive it forward. I'll happily play Devil's advocate if need be. :D

Then the ethics in purgatory are more black and white than on earth

Sounds like a good way to run Purgatory. You can't do any act of evil or commit any sin unless it's obviously your choice. And since there's nothing in the Bible that should let us assume you can suddenly see moral choices in a clear Mass Effect's wheel of choices… seems like it should avoid greys. You can't fall and go to Hell from Purgatory, and generally that's the place where you put the 'good' people who need to either repent for their sins or correct their swerved ways.

Typical superhero is on a personal mission, be it by their choice or by some decree they must uphold. Well written villain (Two-Face is among my personal favourites… and I don't even like Batman as a franchise) on the other hand should reflect something from said superhero's persona. Show the hero to its face how similar they are despite opposite causes or drives, and what they must confront. Both as their enemy and that part of themselves.

I don't know if it can be easily done as a test for someone when the choices are not black and white. Emphasis on 'easily', I never said it's impossible. ;)