You're not supposed to get the ultimate weapons if you're a normal gamer, and definitely not before beating the game. They are rewards for being an insane powergamer wizard who gets fulfilment from bleeding tears grinding for days. FF has a lot of those fans, and kudos to Square for catering to them.
They are way too powerful for the main story anyway. I've beaten FFX three times, I've never got any of them, but it pleases me to know that they're there, making sure that if you want to you can stay in Spira for months.
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