In the first Final Fantasy game, Galenth Dysley tries to lead our characters to shatter Cocoon. Barthandelus, as Dysley, wants to destroy Orphan and all of Cocoon. He wants to reunite the fal’Cie with the Maker.
Notice that Dysley is “the Pope”, or Primarch of Cocoon. His role is to bring back God. But Lightning and the other l’Cies refuse to fulfill their focus. They’re delaying God’s second coming. In fact, they are trying to kill the messenger. This, so far, makes this l’Cie the devil.
But it’s not just here. Later on, Lightning does a short stint as a Knight of Etros, and then retires for about 500 years. Afterward, she awakens to become the Saviour of mankind herself. Her role is to kill the god she prevented from coming into the world 500 years early. She sets us free by killing a god, giving us the means to choose our own destiny.
In any mythology about the fal’Cie, she’d be their devil.
Of course, just because she’s the devil in this world, it doesn’t mean that she’s evil. Not to us at least. She’s evil to the fal’Cie because she threatens them and their existence. And isn’t that really what we consider evil to be? Final Fantasy games have a more or less form of clear-cut morality. The implications for our real life makes our morality more grey in comparison.
Not that the Bible is necessarily real life as far as we know, but who knows huh? Imagine the biblical Satan. He wants to cause as much pain and suffering as possibly can. In order for him to do this, he’d need the world to continue the way it is. In Revelations, one requirement for the apocalypse happens to be Satan commits. Once that happens, it’ll be the end of the world. The end of pain and suffering and the beginning of a new world. Heaven for the good and hell for Satan. So what if Satan, wanting to avoid hell and continue with the evil agenda, just sits on his hands? Thereby preventing the Judgement Day?