Archive Panic: He has more than 1,000 stories on Fanfiction.Net alone which would no doubt take an immeasurable amount of time to get through every single one. To make matters worse, some of them have an obscene amount of chapters which are constantly being added. The two busiest fics are Waluigi's Taco Stand which has over 500 and Life at Pizza Hut which has officially surpassed 800!
Dork Age: Had an Attention Whore period roughly around 2010 where he would deliberately post fics in the wrong sections of Fanfiction.net (Such as putting a Mario story in the Beavis And Butthead section), all of these "dishonest" were rethemed, deleted, or replaced.
Hilarious in Hindsight: He wrote a fanfic about the Nintendo characters (along with Spongebob Squarepants characters) going to Universal Orlando. Guess what happened nine years later (and earlier for the Spongebob crew).
Yoshi Kart has a slew of this. The Koopalings joined in on racing against Yoshi and friends almost a decade before they would do so in Mario Kart 8, which also had Link racing alongside the Mario characters. The Koopalings would later race alongside Bowser Jr. in the upgraded rerelease dubbed Mario Kart 8 Deluxe. Sonic and Banjo would race each other in Sonic and SEGA All Stars Racing, with this being the first time Mario and Sonic characters would compete with each other in a racing sport.
Just Here for Godzilla: Waluigi's Taco Stand and Life at Pizza Hut are the only fics that still get regular traffic, with the rest being ignored.
Padding: A common criticism is how much he spams his fanfics and chapters out, as it not only pushes other authors' stories off the front page, but his own as well. Roughly a third of his stories have few or no reviews because they often get bumped into obscurity before they can even be read.
Seasonal Rot: Between his excessive rate of churning fics out, his constant rehashing of Bait-and-Switch, Random Events Plot and Toilet Humor fics, and his mean-spirited treatment of well-loved characters such as Rosalina, he's lost practically all of the audience he had in the late 2000s and early 2010s. While his older fics have upwards of 100 reviews, his newer fics are lucky to get even one.
So Bad, It's Good: The appeal for pretty much a solid chunk of the fanfiction he writes.
Unintentionally Sympathetic: Rosalina, especially since his reasonings for picking on her are rather nonsensical: He claims she's a "boring Peach clone", yet constantly fawns over Daisy, Dry Bowser, and Toadette, who are themselves "clones" with even less character to them.
What Do You Mean, It's Not for Kids?: Some of his works are rated M. Although there are a few snippets in his T rated fanfiction that have small traces of stuff that aren't appropriate for kids to read.