Which World was altered most by the events of the Game? (Big Spoilers)

[Locke4God]

Which of the FF world's was altered most by what either the villians or the characters had done during the course of their respective games?


A lot changed I know for both 7 & 10, 10 especially. But both endured massive political and philosophical changes. I can't say that much was changed by what happened in 9, just an avoidance of a major change, and frankly in 12, they outright say at the end that things have gone back to the way they were. The same kind of goes for 8, and really the original as well.

But 6!! Kefka literally destroyed the world, and caused and irrevicable change to the entire face of the planet.

Does any other FF title beat what happened there?