I heard it mentioned in a let's play video by the commentators, and then I searched info on it on gamefaqs, and apparently...
If you kill Dedue before he sacrifices himself to become a demonic beast, something different plays out.
Correct.
Killing Dedue post-transformation gives the much better scene. I'm a little annoyed I missed it on my playthrough.
Oh, huh.
In my playthrough I actually saw him transform, but Pulsed back several times trying to figure out how to get Felix over to him first. Because I yet again foolishly assumed there'd be unique dialogue for someone of the same house fighting him (and that this may not happen if he transformed first and couldn't respond), when there was yet again not anything gained by doing this and so I only became more frustrated.
In any case, Felix blasting him with some magic pre-transformation was the death that stuck, so that's what I saw the result of. Which had Dimitri commenting on his death, but I guess he didn't really die (yet), as at the end of the map he was with Dimitri as he died as well...?
In any case, Felix blasting him with some magic pre-transformation was the death that stuck, so that's what I saw the result of. Which had Dimitri commenting on his death, but I guess he didn't really die (yet), as at the end of the map he was with Dimitri as he died as well...?