To make it worse, the reader could find the exact moment Austria finally breaks down. Which culminates in him painfully muttering "I missed her."
There's also the fact that he was Forced to Watchthe apocalypse happen and could do nothing to stop it. And even though the readers themselves know that Hungary's Dead All Along, one couldn't help but think that his Hope Spot actually comes true, if only for his sanity. Then it hits home that the same Hope Spot was almostall for nothing.
A Wasteland Memorial, which is set in the AU's future, could also count. Especially since it shows him starting to go through the same fate as England did in Death of a Nation.
An Ocean of Flame Above is essentially a long, drawn out death scene involving Hungary's last days. What makes it all the more painful to read through is her persistent yet futile attempts to keep on going even as everything in her body shuts down until finally dying.
Switzerland's knowledge of World War III take on a different tone when he realizes early on that Hungary really had no chance of surviving Doomsday. This in turn drives some of his seemingly Jerk Ass actions to Austria in an attempt to keep him from persisting in what he thought to be a pointless search. It's strongly hinted however that it didn't work.
It's also revealed to be a very bitter case of I Did What I Had to Do, especially in the "RE:" version of An Alpine Dawn. While he sincerely thought that destroying much of the evidence was for Austria's own good and survival, he didn't particularly enjoy it.
The Last Minutes to Midnight alternates between this and Nightmare Fuel. Whether it's America's unspoken fears, Russia's realization of who really fired the first shot of Doomsday, or Austria's meeting with Hungary that would never come, the reader knowsit wouldn't end well for anybody.
Prussia coming to grips with the fact that Germany may very well be dead is painful to read through with a straight face.
"We found her...we found her..."
There is one point at the end of Wisps of the Rising Sun where Russia'sStepford Smiler mask slips, revealing why he wears a burnt scarf around his neck the entire time. Strongly implying that Ukraine's dead and that he still weeps for her loss.
There's also Austria's musing about the fate of Nations. While a country's memories will live on so long as humanity preserves them, there would be no tombstone, monument or even acknowledgement of the name "Roderich Edelstein" and his personal experience. And that eventually, even his very existence would vanish from historical records forever.
It's strongly implied in A Forgotten Anniversary (set in1967) that Austria and Hungary's hidden encounter might very well have been the last time they ever see each other before Doomsday. The fact that they promised each other that they would be together only makes it all the more painful.
One fic has America trying to come to terms with the fact that he and his people are going to die in Doomsday. and yet not only does he take it well, but thinks fondly of The American Dream enduring the nuclear hell to come just as the bombs fall.