I have to say overall Tidus. More than white text or flailing of the arms can convey, the fact that you see the pain in Yuna's face itself with her expression just makes it hit that much harder, her tripping and falling trying to get to him just makes it like a torture scene it's just so emotional. Although I'm sure some people consider it to be a torture scene for other reasons....

Pre-facial expressions, the hardest hitting might be Shadow, his whole backstory, haunted nightmares, and ordeal in the game is just so smurfed up. The dark nature of the original japanese dialogue also makes it a really hard hitting and eerie experience.

I don't know if I was ever happy to see an FF character go... I remember wishing Quina bit the bullet a couple times when you lose her just because I thought she was so annoying the first time I played it.