I've come to NG for years now, sadly I had just decided to make an account this very moment, the bright side is that it was your music, this song that I chose to. It is brilliant! Absolutely astonishing, my friend. If you still have all of the left overs from it you should work on top of it. Think of this actually in an Action/Adventure title, not being the final boss music per say, but the music leading up to 'it' the epic struggle for an even greater struggle, you could add so much more intuitive story construction with THIS song. Maybe even add a heavy kick to add to its brutality or clear up that guitar, separate it (guitar) from the rest of the piece in its own tandem moment as lead over the horns and synth-sounding pieces.
Like I had said, this being the leading path music to the "final showdown" into this ominous emotive soundtrack that would make you pee yourself from its introduction, then BLAM! BOSS BATTLE ACTIVATE... I'm not even sure what to say actually, words can't sum up what in my head. I'm not trying to be off topic, I am just amazed. You are indeed brilliant.