Dante has only one worth mentioning thing left in his arsenal that helps him to bring the fight to at least stalemate- Royalguard style and hope that counerattacks would really help (it blocks even environmental damage in the game and one of the most useful styles).
Maybe Doppelganger may be useful- but it's just winning a couple of seconds and handy position to attack by using an invulnerable decoy (I go by combinating styles which is brought into gameplay in upcoming DMC4).
If using Royalguard possibilities wisely, Dante's going to beat Terra at least 6-7\10.
He most likely has another form or some mysterious power since we see his eyes turning a different color once he looks up at the moon heart...whatever source of power in the sky.
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Maybe we'll meet again... Wandering Flame (one of the best pieces in the Final Fantasy X soundtrack)