First, speak goddamn English.

Second, the cheap way: use the W-Item trick to give yourself 99 Megalixirs.

Third, the honest way: put Ribbons and ultimate weapons on everyone, Mystiles on as many as you can, and get every limit break. It doesn't take that much time to get Omnislash; if you select the correct handicaps, it can take as little as three rounds to get the 32,000 points required to buy it. In order to accomplish this, press the Square button to stop the reel; press X when the choice immediately after the one you want has left the center of the reel and you should get it. With a Ribbon equipped, the majority of status effects will be nulled. Try to avoid getting Level Down, Break Accessory, and Seal Items, and if it's available, ALWAYS select Break All Materia in the last round, as doing so will net you 10,000 BP (if you select it earlier, it won't give you as many BP). If not, select Break Magic Materia, as it gives you about 9500 BP in the last round.

Since you don't have KOTR and nobody's at level 99, Safer Sephiroth will only have around 80,000 HP, which means a few attacks plus an Omnislash will do him in. Use a Megalixir immediately after you beat Bizarro Sephiroth, and then start smashing his face with regular attacks. Your Ribbons and remaining Megalixirs will protect you from Supernova, and Cloud should have taken enough damage to perform Omnislash in only a few turns. All you have to do is keep him alive long enough to use it and Sephy's a goner.