I have completed a 2.1 million word megacrossover, currently the largest completed fic on this site:

TSongs of the Spheres

• MLP: FiM
• Equestria Girls
• MLP: Movie
• Adventure
• Drama
• Sci-Fi

Twilight Sparkle comes across a strange black ball with the power to travel to other worlds.

• Violence
• Gore
• Death
• Profanity
• Crossover
• Human
• Sweetie Belle
• Other
• Main 6
• Sunset Shimmer
• Starlight Glimmer

GMSeskii · 2.1m words  ·  590  47 · 17k views

Inside, we have...

• A massive multiverse
• Multiple pony continuities
• Dozens of franchises from Stargate to Jojo's to Homestuck to I can't even list all of them it's so many
• Over a hundred years of in-story time!
• "Movie-length" chapters
• A lot a lot a LOT of characters
• Philosophy!

-GM, master of SotS

• Some of the best worldbuilding ever
• Foreshadowing events a million words ahead
• Memes!
• More metafiction that in Kurt Vonnegut's entire writing career
• Gratuitous tragedy!
• Chronicle of a rise of a civilization
• ADVENTURE