Coredegon

Coredegon is a rogue Mechtogan and the main antagonist of the second arc of Bakugan: Mechtanium Surge. Out of all the villains in the Bakugan anime, Coredegon is by far the cruelest, as he killed many lives, human and Bakugan alike (though most of these murders are undone towards the finale of Arc 2).

History
At the start of the second arc, Coredegon is seen killing Fury, the Bakugan who created Coredegon, despite his creator's protests. After killing Fury, Coredegon states that he is a Mechtogan with his own free will as Slycerak, Exostriker, and Mandibor, 3 Mechtogan just like Coredegon that are later revealed to also have been created by Fury. Coredegon, Slycerak, Exostriker, and Mandibor are soon confronted by the Nonet Bakugan, a group of evil Bakugan that were banished to the Doom Dimension years ago that consist of Betadron, Kodokor, Mutabrid, Spatterix, Stronk, Balista, Worton, and Tremblar, where it is subsequently revealed by Mutabrid that Coredegon, Slycerak, Exostriker, and Mandibor are mutated Mechtogan, which is why they are able to survive without a Bakugan host. Rather than kill the Nonets, Coredegon and his fellow rogue Mechtogan reveal that they intend to head to New Vestroia to kill all the Bakugan there so that they can begin a new age of Mechtogan. However, Worton (the spiritualist of the Nonets) informs the rogue Mechtogan that the Bakugan have moved to Earth. Despite this new suprise information, Coredegon decides to go to Earth instead of New Vestroia with Slycerak, Exostriker, and Mandibor, but leaves before Worton could tell them about the Bakugan Battle Brawlers. Coredegon and his allies quickly arrive on Earth, interrupting the match between Dan Kuso and Gunz Lazar. Upon arrival, Coredegon comments that he heard the Bakugan lived on Earth now, but didn't know that they were "letting themselves be stared at like circus animals", and blasts Reptak back into ball form after Reptak explains that battling involves rules and honor, and isn't a circus, which Coredegon could care less about. After Slycerak notices how a Bakugan goes into ball form after being defeated and Mandibor wonders what would happen if they were blasted while in ball form, Coredegon decides to test the theory, resulting in a battle with Dan, Marucho Marukura, and Shun Kazami. While his allies are quickly knocked down at first, Coredegon is much more resilient against Dan's partner Bakugan, Drago's attacks. However, Coredegon is overwhelmed after Drago increases his speed, prompting Coredegon to combine with Slycerak, Exostriker, and Mandibor to form Mechtavius Destroyer. Despite the massive power boost, Coredegon and his allies are defeated when Dan and Drago summon their own Mechtogan Destroyer, Dragonoid Destroyer, and is about to be sent between dimensions for eternity, when he notices Gunz unconscious after Exostriker knocked him out, and senses Gunz's aura of hatred towards the Brawlers. Coredegon then gets the idea of taking that aura and repurposing it. As a result, Coredegon is able to stay on Earth in a new form based off Gunz's darkness called Wiseman. Coredegon then took Gunz to a volcano, and returned to the Doom Dimension to enlist the help of the Nonets by promising them vengeance against Drago, the descendant of the original Dragonoid who banished them to the deepest depths of the Doom Dimension, since Coredegon's defeat at the hands of Dragonoid Destroyer somehow stripped him and the other evil Mechtogan of their independence. Under his Wiseman persona, Coredegon would battle against the Brawlers several times, only to lose despite using the Nonets to access his true form and summon his allies. However, Coredegon grew stronger with each battle, acquiring the shielding system that regular Mechtogan have in the process, and even managed to beat the Brawlers once before his identity was revealed. During his quest to regain power, Coredegon, in Wiseman form, used his resemblance to Gunz to fool the Brawlers into thinking Gunz was Wiseman, and managed to steal three of the new Battle Suits that Mira Clay developed. Ultimately, Coredegon generated enough power to restore Slycerak, Exostriker, and Mandibor's independence, and later regained his own during a battle against the Brawlers on his own hideout of Volcano Island. Shortly before this, Coredegon killed Balista for discovering Gunz. After revealing the fact that he used the Nonets and the murder of Balista, Coredegon gave the Nonets a decision to return to the Doom Dimension or die. Coredegon then abandoned the Wiseman persona and transformed into his normal form, nearly killing Gunz and the Nonets in the process, and engaged the Battle Brawlers in another battle with Slycerak, Exostriker, and Mandibor. Unlike most of his previous battles, Coredegon was able to win after combining into Mechtavius Destroyer, but felt unsatisfied with simply killing the Brawlers, instead banishing them to the Doom Dimension. Afterwards, Coredegon fought Gunz, who assumed the Wiseman persona himself, and the Nonets, killing and absorbing most of the Nonets except for Betadron, who fled with Gunz, and Worton, who returned to the Doom Dimension. However, Coredegon's arrogance would prove to be his undoing, as the Brawlers (including Gunz), would travel back in time after seeing what he would do if unopposed. During the final battle, Gunz and Reptak created Chromopod, a new Mechtogan, which would signal the end of Coredegon and his allies, as Dragonoid Destroyer accessed his full power and obliterated Mechtavius Destroyer.

Unaltered Timeline
Had Coredegon not been defeated, he would have destroyed Bakugan City, New Vestroia, Neathia, Gundalia, and Vestal.