Ultimecia was the worst boss of all FF games. You could one shot her even easier than you could sephiroth.
Plus she was developed horribly "Hey here's some witch in the future we're mentioning now for the first time, she's got control of time or something, go kill her now, she's the boss, go"
Yeah, I was getting into Edea, thought she was turning into a good villain, then they shit on her and gayed her out. Then I was like "Well, guess that means Seifer is the main villain, that's cool, makes sense, the villain is usually the counterpoint to the hero, which Seifer was" then it turned out to be some witch from the future that was introduced about an hour before you fight her, in one longwinded dialogue. Made me sad.
At least Sephiroth was well developed before you faced him. They just threw in Ultimecia. You knew nothing about her. Edea would have been much better.
Ultimecia is BULLS**T! Edea and Seifer were cool, I was convinced one of them would be the last boss, but no, the developers thought it necessary to make the last boss some sorceress no ones ever heard of and introduce her damn near the end of the game. As for who would win, although Ultimecia's magic is better, Sephiroth's isnt too shabby and has vastly superior combat abilities. I also found her easier. So Seph ftw.
What would have been better is if Seifer had followed squall and his gang somehow ( " I wont stop until your dead ! " ) and then usurped Ultemecias power ( "Foolish boy..my control of the the time stream...it's..interrupted..nooooo" ) it would have been a sweet twist ending and saved all the bulls*it with Griever....
FFIV basically did the same thing. You think the last boss will be Golbez but then you learn about Zemus. But the thing is that they just didn't spring it on you at the last minute. Even before Golbez became a good guy you learned of Zemus when FuSoYa joins your team.