I found Ozma to be one of the easiest optional bosses in the series, but I still thought it was no pushover. I went after it after one of my friends managed to beat it and started bragging of having done it before me, but whined about what a long and difficult battle it was, having to deal with it using so many Curagas on itself, hitting his party with Curse and so on.
This struck me as a little unfair of him to brag about as I didn't even own the game myself, so I borrowed it from him, played it through, and took on Ozma myself, with a party of Zidane and Freya for damage, and Quina and Amarant for their Auto-Life abilities, as well as their damage-dealing skills being none too shabby.
Despite getting kicked to the curb pretty badly, I only took two actual attempts to beat it, the successful of which only taking two full rounds thanks to me spamming Thievery, Dragon Crest, Frog Drop and No Mercy.
I reckon this boss would've been a lot more challenging if they'd thought to give it a few more HP, but whatever.
Share your Ozma stories, people!