I like the vivid detail of Shuyin's repeating nightmare (I always loved this aspect of the Den of Woe), because recalling his worst possible outcome, over and over, without respite, really would drive a guy insane.

I liked the slipping of his memories, the slow contamination of everything he holds dear, while also showing the first strains of his ultimate goal in FFX-2 - erasing Spira, along with his own mistakes, to find the peace he seeks.

(I actually really like Shuyin as an antagonist, in case you couldn't guess, so I love that you chose to write about him! I considered him myself for my answer).