Immortals Fenyx Rising

This is story related and cannot be missed. During the Balance quest, where you "Complete the Final Offering".

The only reason I'm making a guide is to let you guys know that there basically isn't a point-of-no-return. Even after the final boss which I'll add here in spoiler tags:

After that you're free to run around and do the other achievements. Before you reach the Final Offering, Athena will let you know to do anything you still have to do before using the altar behind her, which pops the achievement. You can hit Continue or Load your last save afterwards to mop up anything you may have missed.