Ere when she finds out that Report is still alive.
A dying Sir Romra offering his helmet to Naharrud, so the latter could finally read all those books like he wanted.
Regnis's death. Oh God.
"My song... and my love... don't forget them..."
Made even worse by the previous pages, where Gabe repeated tries to use his powers to heal her, repeatedly getting hit by his own Lightning but not giving up, only to fail in the end.
Ere (again) in the "Worst Case Scenario", only this time she killed Report with her own hands.
Even more heartbreaking when she and Neeuq make their way out of the factory and the normally graceful and competent Ere is completely disoriented, stumbling into every obstacle along the way but still refusing to let Neeuq help her carry Report's body.
Also, when she is dismembered and Left for Dead by Dab Gib and uses her only remaining hand to crawl over to Report's body and hug it before dying herself.