She would be highly succesful during her serious 21 type of era (FFX), with the GP loving her and opening with HUGE sales, being remembered as one of the most iconic pop acts in the game. Then, she would release a fun, mindless and over the top record and she would flop, her game not even being critically acclaimed (X-2). Then, years later, she would announce a comeback with a more back to her roots sound, claiming that her last underperforming album was just a mistake, that it wasn't really her, but nobody would care and people would have moved on from her (X-3 tease at the HD collection).

She would be collect the lessors easily.

FFX(Her 21 era)
FFX-2(Her TD Era)
FF X/X-2 HD (Her Prism Era
FF X-3 (Her R8 era)

Technically, Real Emotion wasn't Yuna, but LeBlanc.

She'd be an underdog at first, but climb to the top against all odds and revolutionize pop, after which she'd fall back a bit with only her diehard stans supporting her later work.

One of which would be me, I actually enjoyed FFX-2.