The recent Kirby games have really nailed it. The final bosses have been insanely epic and the music has been one of the reasons why.
The most recent game, Star Allies goes from this.
to this
then the final phase of the fight when we see the final boss true form and realize this creature is somehow related to Kirby, we get this.
Lets not forget the madness of Planet Robots final boss
Phase One
Phase Two
Phase Three
And the last phase that only happens if you're playing on the True Arena
Might as well bring Triple Deluxe since it really nailed it as well.
Phase One
Phase Two
Final Phase