Testing Yu-Gi-Oh decks for a story. The first round of a tournament features the three main characters of the story, using Zombies, Jurrac and Crystal Beast decks, facing off against a team of My Little Pony cosplayers - Fluttershy, Twilight Sparkle and Rarity, using Naturia, Spellcasters and Gem-Knights. I was only half-serious when I was building their decks, because I meant for them to be joke characters.
The pony cosplayers won three times each against their tournament opponents, and the protagonists are therefore going to lose in the first round of the tournament. Now I have to retcon them into being national-level duelists, and I am laughing my ass off at the fact that I accidentally made three decks that completely kick ass, while simultaneously derailing my own story.
Zombies should be able to beat out those guys with things like Zombie Master. Jurracs would be powerful if you sneakily allow in stuff like Rescue Rabbit and Evolzars (hey, they're still dinosaurs, riiight?). As far as I can tell crystal Beasts work if and only if you just constantly summon Pegasus by any means necessary.
Also you're in luck in that some of Naturia's key cards are poorly designed to such an extent that their effects almost always fail.
My zombies never stood a chance - I ended up facing down what could've been an OTK on my first turn. Topaz, Ruby and Garnet out in the first turn of the game. Particularly irritating since I've used that particular OTK before.
Evolzars, IIRC, only get their effects when they're Tribute Summoned using Evoltiles. Plus the duelist using them is canonically terrible at the game anyway. (Canonically as in in the story, not as in they're a canon character.)
Also, the guy I was testing the Naturia vs CB with runs a Naturia deck online anyway, and he is
brutal. He managed to completely lock me down within five of his turns - Bamboo Shoot, Landoise and Mantis, with an Exterio's Fang and Bottomless Trap Hole facedown.
Also also I have very little experience with Jurrac.