Most upsetting incident in Quenta Silmarillion

[Turgon of Gondolin]

For me the two most upsetting events in The Silmarillion were what happened to Húrin and the entire fall of Doriath.

It wasn't Húrin's capture, per se, it was how Morgoth abused him and finally, setting him free, twisted everything he saw, heard, and knew, until ultimately the truth was revealed and he was broken. This was Morgoth's cruelty highlighted in perfect form, with no other motivations or reasons wrapped around it—cruelty for cruelty's sake.

As for the fall of Doriath, the death of Thingol and the departure of Melian, leading to the fighting between the Dwarves of Nogrod and the Elves of Doriath, followed by the deaths of Beren and Lúthien, which opened the doors for the sons of Fëanor to invade and commit fresh murders … all of this together is one of the most horrible culminations of events, for all of it was caused by greed for a worldly object.

If we change "upsetting" to "tragic", though, I think it would have to be Fëanor's pride in the Silmarils which led to him denying them to the Valar, which led in turn to everything else—that's the greatest tragedy of all, I think, for in this we see the marring of Fëanor who was—like him or not—something special and unique in the history of Arda. That said, I believe this was a necessary tragedy, for without it all the events that unfolded after may not have been possible. We can't know, any more than any of the Valar, what was in Eru's heart for his Children. It may have been that Fëanor played one of the most important roles in the unfolding of Eru's third theme.

 

[Mouth_Of_Sauron]

I had to go with Other. If there wasn't an Other, I would have gone with that bit about the Dwarves and elves fighting over the Nauglamir. Mablung, one of the few upstanding citizens that I'm able to admire, died because of that. And, also, a bunch of Dwarves. The most upsetting thing wasn't on the poll, though. I don't know why.

It is ---> The murder of Mim. Mim was cool. Just a little guy, never did anything evil to anybody. Got kicked out of his home for nonconformity. Got kicked out of some unfinished caves by some arrogant elves. Found the superly cool Amon Rudh but had a bunch of human bandits force their way in. It took a while, but he got past his righteous fury of having his home invaded and his livelihood constantly jeopardized, and he started getting friendly towards Turin elfbane. But then, Beleg showed up. Mim was understandably displeased at the sight of some elf. He was forced to deal with that thing lazing about on his furniture, but he continued to gather food for too many mouths. In the same situation as when the bandits caught him, some Orcs forced him to reveal his home again. With his secret out to apparently everybody, he triumphantly made it all the way back to Nargothrond, against plenty of odds. Nobody else could withstand the blight left by Glaurung. He was as close to happy as he'd been in far too long to keep an ordinary sentient sane. Then Hurin showed up. I don't mind Hurin, either, which makes it sadder that he murdered Mim for no good reason. Mim was unarmed and attempting to calm the terminally depressed guy down when Hurin gutted him. Not cool. Very sad. Nobody cares. *sniff* Poor Mim.

I predict that Beleg getting killed will win, though. Ugh.

not to mention his son slain by the very people he was attempting to aid! poor mim will always have a place in my heart and one of the oft-overlooked characters in the quenta. though poor mim's treachery proved ravenous, it was out of complete despair. one can only ask so much from a humble Naugrim who knows nothing of the blight of Men and Elves who is suddenly thrust into matters over his tiny bearded head.

 

[King Naugladur]

For me, the most upsetting was the murder of Mim by Hurin.
Mim had a right to the hoard of Nargothrond, because his ancestors had delved the halls of Nulukkizdin before the Noldor came from Aman and settled the lands of Beleriand. Since Mim was unarmed, it was a cold-blooded murder by Hurin, which mars his heroic image. However, I try to console myself saying that Hurin was still under the curse of Morgoth, which Melian later took off him.
King Naugladur.