Well, if I were a boss in a JRPG, there is only one track that I could choose.
Tell me that wouldn't make you think the boss you're fighting is going to be one tough sunuvabitch.
If I were a recurring boss in a JRPG, the first encounter would be set with this, possibly an instrumental cover though I'm not sure it would have the same effect without the lyrics:
If I were a Sephiroth-style baddie with a final, non sequitur always-lose battle with the protagonist before the end of the game, that particular fight would be: