-A Mime Materia and a mastered Knights Of The Round summon materia is required for this trick. First, cast Knights Of The Round with one character and then use mime with a different character. Savior Sephiroth should be defeated in those two hits.
-You will need to have Mime command, W-Summon, Knights Of Round summon, and Quadra Magic. Master Knights Of Round. Equip this with Quadra Magic and W-Summon on Cloud. Equip Mime on another character. This trick will have to be repeated if the other character does not attack right after Cloud. Use W-Summon Knights Of Round two times and he will use it eight times. Quadra Magic must be at second level. After that, use Mime and your other character will use it eight times.
-Put the Enemy Skill Materia (can be found in the Green Chocobo's stable at the Chocobo Sage's house) on your best magic-using character, then put the Long Range Materia (found after defeating the Materia Keeper in Mt. Nibel) on your best attacker. When Sephiroth uses his Shadow Flare attack, whoever has the enemy skill Materia will learn it. After that, cast it on him only when he floats up in the air (to conserve MP). Make sure whoever you put the Long Range Materia on does not already have a long range weapon (for example, Vincent or Barret), or it would be pointless. Put it on your best attacker so that they can damage him even when he is floating.
-Have two characters in your part have Mime, and the other with W-Summon connected to Quadra magic . This allows you to use any magic or summon six times in a row. Have the two people with Mime use it, then have the last one use Knights Of The Round on him. This will result in eighteen consecutive Knights Of The Round hits. Heal your HP and MP, and repeat the summoning. Note: This isn't an instant killer.