This would be more than just a catastrophic situation, this could be flat-out APOCALYPTIC for Equestria. Also if someone like Princess Luna was turned into something as evil as nightmare Moon, then I would CRINGE to see what Celestia would turn into. I would think that Celestia would be a lot more powerful than Nightmare moon since She can control fire and the sun shrike nightmare moon cannot. any thoughts or predictions on what an evil version of Celestia would look or act like?
Nice, but the truly evil version of Celestia is pretty much canon and looks like this: Spoiler :Trollestia:
Strictly speaking, it's not required that the ill will be directed at Luna. That having been said, the probability of such being canon is rather low.
Celestia can control fire? Since when? Even if she became Solar Flare, wouldn't she be just as powerful as she kind of is now? I mean, do we know that Luna became more powerful as Nightmare Moon?
We know that Nightmare Moon was powerful enough to challenge Celestia. The answer to you question is the inverse of the answer to the question of whether Luna is able to do the same. Would that have caused Luna to banish her to the sun? That would be rather unpleasant with a faint hint of burning.
