LL = Low Level (limit = 29)
NM = No Materia
NI = No Items
I'm pretty certain you didn't see this one coming. I actually did this last week, but decided to uploaded the Game Over video anyway for the fun of it.
What makes this battle possible is another one of Cait Sith's Slot combinations. Lucky Girl makes all attacks deal critical damage and that erases the problem of dealing enough damage. Getting Lucky Girl is much harder than getting Mog Dance, though. Getting the first heart is easy, but you can't just press the button and get the next two. I honestly don't know exactly how it works, but it's much harder. Other than that, the battle isn't all that luck reliant.
This is how the battle must play out in order for you to win:
Beginning: You might get a chance to use an attack or a limit break before Sephiroth's first turn, but it's very important that you don't. Sephiroth casts Wall on the first turn and you need it to run out as quickly as possible. With ATB on Active, time never stops and his Barrier bars will empty during attack animations.
Wall: Cloud uses Climhazzard, giving Cait Sith enough time to input the right combination. Yuffie attacks for normal damage.
Shadow Flare: Yuffie will reflect it and it has a 60% chance of missing Cloud. If used on Cloud, it must miss. Cait Sith is allowed to die, but it makes the battle more luck reliant later. Sephiroth's Barrier has run out and the party attacks for critical damage. Cloud must go first, so that he can defend again in time for Wing.
Wing: Used on the character with the highest current HP. Cloud survives with Sadness and Defend. Yuffie and Cait attack for critical damage.
Ascend: Sephiroth wastes a turn and Yuffie can attack for critical damage. Cloud and Cait don't have long range weapons and cannot reach.
Pale Horse: Instant death. Must not be used on Yuffie. Preferably used on Cloud. Yuffie attacks for critical damage. Make sure to select the next attack commands before Super Nova, starting with Yuffie.
Super Nova: Deals 93,75% damage and might inflict Confusion, Slow and Silence. Yuffie (and Cloud if alive) must not get confused. Yuffie attacks for critical damage, followed by Cloud or Cait trying to attack, allowing Yuffie to use her limit break on this turn. If Cait is alive, use his limit break as well.
Break: Deals 0 damage to Cait and Yuffie reflects it. Has a 60% chance of missing Cloud, but he is allowed to die now. Heartless Angel is used instead if Sephiroth's HP is less than 20000, but it is completely harmless. Yuffie attacks for critical damage or uses her limit break if she was the sole survivor after Pale Horse.
Descend: All surviving members attack for critical damage. Battle ends here if none of Yuffie's attacks missed and either Cait used a limit break after Super Nova or Shadow Flare was reflected to Sephiroth.
DeSpell: All surviving members attack for critical damage. If it didn't end at Descend and none of Yuffie's attacks missed, it ends here either way.
Deen: If for some reason you should see this attack, Sephiroth wins. It will not miss.
Note: When I have Cait attack out of reach, I'm simply manipulating the RNG. If I hadn't done it, Yuffie would have gotten confused by Super Nova.
Note2: The only difference from the other battle is Cloud having Sadness. All the equipment is the same and the Bizarro battle has not changed at all. Cait had more HP this time, but that's simply because he was defending the last time he got attacked by Bizarro.
All characters: level 29
Well, that concludes another challenge, and a challenge that was thought to be impossible without the use of Game Over. However, both Carry Armor and Safer-Sephiroth fell at last, even though it required some luck.
And that, as they say, is that. Thanks for watching!