This will probably leave you baffled, in the low level game, vanish / doom trick for bosses is PROHIBITIED, you have to win fair and square, no throwing super balls, no using bought rods for spells, etc.

At the last boss my party is all level 7 and they have about 150-200 hp. There is ALWAYS some way you can set up your party to win, regardless of level. As SharkESP says in his guide, you will lose if you are not prepared, not because you are not a high enough level. There is always some way to win even against that damn Imperial Air Force (God that was a pain in the ass)

This challenge has been a really rewarding experience for me, it's easily the toughest FFVI challenge, if anyone is interested in starting a lowlevel ffvi game, let me know, I'll be happy to get you started and give you more tips than you'll probably ever want to hear.