The Grand Finale is the final story arc of Season 29. It revolves around the Heroes of Legend and their allies' fight against Sasuke Uchiha and Mechtavius Destroyer as the latter launches a full scale war on the multiverse. Later in the arc, Fabia Sheen, who was zombified during this arc, hijacks the Smash Bros. Galaxy engine, using it to transport the planets of the multiverse into the Smash Bros. Galaxy, and deposits all the residents of every world onto Earth, causing more chaos, which provides Mechtavius Destroyer with his final energy boost, fully ressurecting him at last. After his revival, Mechtavius Destroyer banishes the heroes to the Doom Dimension after they attempt to fight him on their own, and then proceeds to kill and absorb every villain except for Sasuke Uchiha and Yami Bakura. Due to this, King Kai gathers every hero and villain on Earth to make a final stand against Mechtavius Destroyer. Later, Mechtavius Destroyer absorbs Sasuke and Yami Bakura to stabilize his infinite power, though a new set of them are released shortly after. Later, Master Hand tells everyone about The Creator's Triune, and increases the power of Naruto Uzumaki, Goku, Sonic the Hedgehog, Sasuke, and Yami Bakura to put them on par with Mechtavius Destroyer. At the end of the Grand Finale, Mechtavius Destroyer is finally killed for good by Naruto, Goku, Sonic, Bowser, Mewtwo, and Dragonoid Destroyer.
- A war between the multiverse begins.
- Sakura Haruno betrays the Heroes of Legend and joins Mechtavius Destroyer.
- Fabia Sheen and Ren Krawler are zombified, but Ren is later cured.
- Mechtavius Destroyer is fully ressurected, but is unstable until he absorbs Sasuke and Yami Bakura.
- The League of Villains (excluding Sasuke and Yami Bakura) are killed and absorbed by Mechtavius Destroyer, but are ressurected when Master Hand releases a new batch of them.
- The Heroes of Legend and every friend and foe they've met, as well as several other heroes enter a series of battles against Mechtavius Destroyer.
- Sasuke and Yami Bakura are absorbed by Mechtavius Destroyer, but are ressurected through a new batch released by Master Hand.
- Zombie Iron Man is killed while making a final stand against the zombified Fantastic Four, but manages to kill Zombie Sue and Zombie Torch in the process.
- Zombie Wolverine sacrifices himself so the Heroes of Legend can escape, find their friends, and save the Earth from Mechtavius Destroyer and the zombies.
- Colonel America ruthlessly kills Zombie Reed and Zombie Thing after they continue to ridicule Zombie Spider-Man.
- Mechtavius Destroyer is killed again, but is revived in Season 30.