We don't... really know what happens to Nerdanel, tbh. She drops out of the story once her family marches north. She is presumably still alive and well, if grieving.
Celebrían goes through absolute hell during her last year in Middle-earth, but her actual ending is presumed more or less happy, if bittersweet because at least one kid never sees her again.
Amroth gets a tragic ending, and he had to know it was suicidal to try and make that swim. He drowns in a choppy sea trying to swim back to his lost love.
None of my Thedosians have reached their endings yet, tyvm, but Ingrid is the only one I think will get an actually happy one.
Isabela is not the sort to die a little old lady in her bed. She is going to die in a duel or a shipwreck or something like that.
Kalli... is an elf mage. Whatever she ends up doing, she's going to have a difficult life and best-case-scenario is an unremarkable death.
There's Edgar, who is presumed to get a happy ending... but does he? Like. He literally dies in canon, and though he can be saved with a cat's extra life, he can also permadie.
I mean, in theory, he's alive and well and serving as Prince Consort in Daventry and raising (and probably spoiling) his son Gart--but what if he only got 20 more years from the cat? We don't know.
And if he is still immortal, eventually he's going to have to bury his wife and child.
And then we have myth kids.
Most are deities, so, y'know. LOL WHAT ENDING.
But Apollo is doomed to have ever love affair end badly.
Ogma is supposed to ultimately die in battle.
I don't think Sif's fate in Ragnarok is ever specified, but she's probably doomed to die horribly.
Kali may or may not literally tear the world apart.
So, plenty of fun stuff there.
Though... When it comes to old characters not on the muselist, I think Cullen Hywel's ending takes the cake.
Granted, the dude was batshit nuts by the end, but he ended up physically imprisoned in his own insane mind.
I mean, to protect everyone from him, his mother (who is a fae) opened up a magic portal that led straight into his consciousness and made him go through it. He is bodily trapped in his own mind.
My money's on Amroth, for the angst of it.
then again, Nerdanel, given all she's seen and what she knows her husband and sons did/do...ow
Heartbreaking elves~