Final Fantasy X-2 
Game Endings Sad Ending
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Warning: Contains major spoilers.If you do press X and activate the secret event, but you don't have enough story completion, you'll get the the sad ending.
Yuna will hear a whistle and she looks around to hear where it's coming from, pyreflies will gather form into a hologram of Tidus. Yuna will tell him that she had been always thinking of him and has now finally gotten to meet him again. But, she's okay now. As long as he's here in the Farplane, she can come see him whenever she wants. Tidus dissapears and Yuna walks off, then you see the normal ending. THE END.
Note: Some endings require a certain amount of game completion to activate.