The Galacticmon fight in Digimon World 3. It starts with the last boss you just fought fusing with the space station you're in. So you run outside and fight starts with you in my middle of space. And the camera pans behind your team and you see you are literally the only thing between that and Earth. THat becomes more apparent after you beat the tail and while making your way to it's core, it launces an attack at the planet and whoever you have out takes it and it leaves it with 1HP and then the final battle starts with a more heroic version of the main theme playing.

Luke vs Asch near the end of Tales of the Abyss. I love The Meaning of Birth.