FinalHeart
Svegli
I had the most trouble with Safer/Savior Sephiroth. It's probably because I had no ribbons and had no desire to go hunt down a Master Tonberry, and morph it. After I lost a couple of times I went back and got Cloud's ultimate weapon, as well as actually finding a W-Magic on my way back. That W-Magic actually helped a lot because a double cast of Ultima is what ended up killing the bastard.