I was figuring out why Squall`s face had a black hole at the end of the game, and I`ve finally concluded ...
Compared to
See the similarity? Ultimecia had white/bright yellow light on her face and black light on Squall`s face.
When Ultimecia began compressing time, everything become disorientated. Specific timelines from past, present and future being interrupted with each other. The game says that time compression is dangerous = you will expect unexpected occurrences. I think this is the reason.
EDIT- During that fight, there`s something strange on her legs. It looks like Anima which I think make sense because Anima represents a sign of being aggressive. Ultimecia was being aggressive at that time too.