I'd consider the Sundering to be far worse in terms of the broader consequences. Hermes and Meteion may have set everything in motion but they could have been stopped simply by Venat speaking up and sharing the knowledge that she held.

I'm pretty sure that it's illegal in many countries to withhold information that could help solve or prevent a murder. How interesting, then, that the game ordinarily loves copying and pasting real world concepts of morality and 'justice' right up until it comes to something that might make Venat look like a complete psychopath.

Speaking of which, it's funny how often the game trots out this particular line of dialogue:

"To ignore the plight of those one might conceivably save is not wisdom—it is indolence. And such a passive stance will not, I fear, take us far upon the path to progress. That you would spare these younglings the horrors of war is a decision with which I am in full agreement. Thus do I refrain from exhorting you, or any other, to return to Eorzea at my side. We must all protect that which we hold most dear in the manner of our own choosing." - Louisoix

How strange, then, that the Ancients are so heavily criticised for doing everything possible in order to protect and preserve their loved ones instead of...rolling over and allowing themselves to be wiped out and have all memory of their existence eradicated.

Worse yet, the promise to 'remember us' can't even be honoured because the game falsely presents Zodiark as being an 'ill-fated wish' instead of the very thing that ensured that Unsundered and Sundered Etheirys actually survived long enough for Venat's silly gamble to pay off.