That's a tough one. One Winged Angel is not my pick, simply because it was a little too dramatic and got corny. Not that it was bad at all, just overdone.

Let me see, my contendors would be The Last Battle, the last segment of Dancing Mad, The Extreme, Final Battle, Decisive Battle. Tough decision, but I would go with The Extreme. I like it's climactic build-up, and I think it goes well with the final boss. That's my vote.