Thank you for your feedback!
Indeed I didn't intended anything scary or creepy for boss fight music, as it's designed for a JRPG genre with a heavy emphasis on the fantasy side which for me is represented to the audience under a theatrical interpretation(with a certain distance) rather than a 'simulational' sound design.
I would however totally do, in this same soundtrack, another boss fight music with those scary musics for a boss or area mainly focused on the horror genre as a sub chapter.
But I have decided that, for the final boss of the whole game, epic style music would suit better to culminate the drama after a journey of long hours of gameplay. Hope this makes sense!