Fire Emblem 7: The Fire Dragon

With high stats and an attack that ignores defense, it's certainly intimidating. As long as you make sure it doesn't double anyone and keep everyone's HP topped off you should be able to win through attrition alone. If you have any Luna tomes left, now is the time to use them. Buff Athos with Filla's Might, give him Luna and you can one-shot the dragon with a crit. Good thing there's only one. Imagine fighting more of them.