Dark eaons the quest continues

Okay so you know i killed Ifrit, Valefor, Ixion and shiva already... yesterday i finished off yojimbo.

Ive just finished an excruciating battle with Bahamut o_O
He killed all my aeons quite early on (the battle lasted 2 and a half hours +) Auron is the only character with a celestial weapon which didn't mean much as physical attacks always missed. I learned Blitz ace during the battle but without tidus's celestial weapon it was pretty pathetic. He can break damage limit and has a max strength stat but it still was pretty weak. I relied heavily on auto-life and overdrives and prevailed by forcing him to attack me to build my overdrives. Was the hardest battle ive fought on FFX so far

I now have the crest for tidus's celestial weapon and will race the chocobos for the sigil (ugh) But i still refuse to play Blitzball and get anima or the magus sisters ( just lazyness really) Im sure i can take anima but is it actually possible to beat the magus sisters without them?
Also i have one monster to unlock in the monster arena before i unlock nemesis.... is it possible to defeat him without wakka, anima and the magus sisters?