People, when we see events playing out differently (such as Last Order's depiction of the Nibelbeim incidents as opposed to the original game's), these should be understood less as retcons and more as different depictions, or interpretations, either told from different points of view or expanded upon. Naturally, some things will be different. Retcons, however, are those
major changes to the story. But things like Tifa discovering her father outside of the reactor rather than inside, Cloud stabbing Sephiroth before he turns around rather than after, Cloud being impaled twice, and Sephiroth willingly jumping into the Lifestream rather than being tossed in: these things are extremely subtle differences in narration rather than retcons.
And Han shot first, damnit! (Pretty much everything else I'm okay with.)