Here's one! It's short. The spelling is terrible. It's pretty clear within a paragraph that it's weird porn fanfic.

"Can you filter by genre or something."

Here's one about the first war, where he was imprisoned for a while?

"Does he get defeated for a second time or are all of the Ardas just blighted hellscapes forever."

Aha, here's one about his eventual defeat by the Valar after all the shit that happened to Matt-and-co. went down?

"Thank you!

They marched in. With an army of people with swords. And one guy with a flying ship - Bar, do you have any books like this from Ardas that have invented the television -"

Sure, here's its analogue from a multiplanet Arda.

"Thank you." He settles down to reading. "...Cam, I think this is pretty much 'what would have happened in Singularity, without you..."

"...do I wanna know?"

"I think you will feel more confident in the rightness of your decisions? On the other hand it is not a pleasant read."

"...okay." Cam makes himself a copy and plops down next to his Maitimo to read it.

They didn't know to be wary of escalating. They landed and opened fire all along the orcish front lines, with weapons unprecedented on Endorë, they took back several hundred miles of land in a three-week-long opening bloodbath. Two years and two hundred million orcs dead later they were finally within in range to take Angband, and that's when all of their new-won territory went up in a series of nuclear bombs. Fëanáro died - and that, opines the author - is when the war was lost, though it lasted nearly six hundred years longer -

"Fuck," Cam murmurs.

"Yep."

"Your prediction was accurate. Fucking noshow Valar."

In the ensuing year without a summer two hundred million people starve. Biological weapons make a whole continent uninhabitable. Maitimo's captured. Findekáno flies into Angband on a suicide server-destruction mission and Manwë helps him get out with a chip that they're really not sure they should bring back. (They do anyway - they need him -)

They work with the Dwarves; they use nukes too; everyone swears to stop that. They get anti-missile systems up, they catch most of the rockets the Enemy is throwing at them, they disperse people into small cities the Enemy can't find. The planet's population falls from 5 billion to a billion over the slow grind of four centuries, and then the Enemy gives Doriath a Silmaril and launches his final offensive. 

"Annnnd the Silmaril thing bites them..."

"Means the Enemy didn't ever figure out how to redirect backups, whatever small comfort that is."

And they level Doriath from a thousand miles away, only to find the Silmaril is not anywhere in the ruins, it's been smuggled south instead...

Ugh. Ugh ugh ugh.

And a ship slips out in the chaos of the fall of Sirion and breaks orbit and there's a vicious fight in space for control of one of the few remaining lightleapers and then Elwing takes her Silmaril and leaps with it, and several years of wandering later she points her ship towards Valinor and begs the Valar to intervene. 

A footnote in the account of reconstruction after the war of the Valar and Melkor notes that the surviving Fëanorians fought their way into the space station that was the base of operations of the Valar, stole the last two Silmarils, and flew into Endorë's Sun with them. 

Hugs for his Maitimo.

Hugs. Lots of that.

"Bar - any like this, but from a world with native summoning -"

I'm afraid not.

"Does that mean he never gets stopped at all."

I have no particular ability to predict the future.