I'm not sure if we're talking about doom, as in the atmosphere, or "Doom" the FPS, so i can't really weigh in on that matter.
But I think that this piece achieves a tragic villain theme, like you intended (based on the Author Comments)
First off, I REALLY LIKE THE WAY THE STRINGS WORK HERE!
They sound so... rough. Like the character, a bit unrefined, unpolished, leading to his "rebel" characterisation. I'd like to see what the piece would look like if the strings were changed to something smoother; and I imagine the piece would not achieve the same darkness, and more of a cinematic, possibly "movie-trailer-ish" sound (not that it isn't already kinda cinematic).
And that Finale was very good! BRAVO!
It feels like the "moment of tragedy" where the character would realise what they are, but its too late to take anything back (well that's what it feels like to me).
I'd like to see more.
Look at the words you made me type!
Adding half a star for inspiring me!