The fanfiction is currently above 16,777,215 words (we don’t know the word count because fanfic.net uses 24-bit integers to count the amount of words and this fic surpassed the computational limit), and is 2000+ chapters. It is written by Jamesdean5842 and is still being written to this day.
The story is about an OC named JD Knudson who moves into the Louds town and goes on adventures with them after creating a superhero team with them. According to the recap (Obviously not even close to finished recap) on Tvtropes.org, the fic is mainly comprised of loud house episode plots rewritten to include the OC and a multitude of crossovers with other franchises from any piece of media you could possibly think of. (https://tvtropes.org/pmwiki/pmwiki.php/Recap/TheLoudHouseRevamped)
Some examples of the crossovers are Ed, Edd n Eddy, Naruto, Dante’s Inferno, Inside Out, Matilda, Pulp Fiction, CatDog, Metroid, The Simpsons. This is a very small selection of the crossovers done in the fic.
Despite the fic’s main characters being minors, the story contains lots of swearing, sex, romance, drugs, and violence. The sheer amount of strange details about this fic is insane, reading the TVtropes page will give you some insane mental whiplash. (https://tvtropes.org/pmwiki/pmwiki.php/Fanfic/TheLoudHouseRevamped)
This is just the tip of the iceberg for this story, it is absolutely insane.
It was started in 2017 and is being updated daily.
According to people who have read a great portion of it, the writing is god awful and does not improve the longer you read.
From what I can tell from Jamesdean5842’s profile, he is quite proud of The Loud House Revamped calling it his “prized work” (https://www.fanfiction.net/u/5625800/Jamesdean5842).
The first TVtropes link I put has a list of the “episodes” that have been documented by readers so far. Each chapter seems to be its own episode of sorts.
The plot itself is not very interesting, the only thing noteworthy about the plot is all the bizarre and absurd things that occur in it, but it is not fun to read. You can see examples of the strange things that happen in the story on TVtropes.
As far as I can tell, there are no fanfics of this particular work, but there is a lot of fan fiction of the Loud House.