This boss battle is cinematic, as evidenced by how all his stats are negative infinity. Cloud instantly gains the
Limit Break Omnislash even if he has not learned it. The Change command to change
row is greyed out, Sephiroth starts with an empty ATB gauge, and Cloud's first physical attack will deal double damage, as if the battle was a
preemptive attack.
If Cloud does not use Omnislash, Sephiroth will attack Cloud which reduces his HP by 31/32, to which Cloud will instantly
counter and win the battle. Cloud is not equipped with a
Counterattack Materia in the battle, but counters because Sephiroth's AI script commands him to. This is evident because if Sephiroth is made to miss (not possible in a normal game), Cloud will still counterattack.
If cheat devices, such as Gameshark or Action Replay, are used to keep the player's
Materia, one can use
Sense on him to find out that Sephiroth has negative infinity Hit Points. Regardless of this, any attack, so long as it does not miss, even using the
Steal command, will defeat Sephiroth.
Sephiroth has only one attack in his disposal, which depletes all of Cloud's health, leaving him with negative infinity HP. It is classified as a magical attack, and thus will never
critical.
If Cloud enters the battle with 7,777 HP, the attacking spree phase of the
All Lucky 7s status will not activate.
While it is impossible to get
Game Over in this battle, it is possible to hang the game in an infinite loop via a cheating device. If one is to set something else than a weapon as Cloud's weapon (a
Protect Ring, for example), Cloud's regular attacks will miss. When Sephiroth slashes Cloud and he counterattacks, he will miss, and Sephiroth will keep on attacking Cloud, but his every attack deals less and less damage until he is doing 0 HP damage every hit.