@TruckOSaurus
You're right, but if you want the real challenge of the final boss fights, you have to get KOTR, since if you cast it on Jenova Synthesis, Bizarro and Safer sephiroth will have more HP and stats. Plus if you're Level 99, Safer Sephiroth will be at it's utmost strength, so the game actually compels you to be at the highest level possible.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
