Deconstructed in Season 4. His latest evolution is causing a massive amount of grief to everyone. This includes causing him and Dan to fall out from grace with their In-Universe fanbase, creating an unstoppable engine of destruction, and threatening to set loose the Sealed Evil in a Can that's serving as this season's Big Bad.
Power Incontinence: Definitely. In the new season, Drago has become so powerful, his power alone nearly destroyed the battle field of Bakugan Interspace (considering the high power levels Bakugan has reached, some would say it is about time). Things get worse later: The power has become far too much for him to control, which is forcing them to concentrate too much on keeping it under control to win matches. Not only that, its now literally created a monster and is threatening to let Mag Mel out of his prison.
Despite the fact that they have now learned to control their new powers, and have taken multiple levels in Badass, managing to summon a Mechtogan Titan recently, which curb-stomped three other Mechtogan within a minute, which occurred through learning to control Zenthon, the energy from their battles has given Mag Mel EXACTLY what he needed to start tearing apart Bakugan Interspace.
Ship Tease: With Alice in Battle Brawlers and Fabia in Gundalian Invaders.
Took a Level in Badass: In Mechtanium Surge, he becomes the leader of the Brawlers when Dan takes off and takes his fighting skills up a notch. Taylean even becomes strong enough to create a Mechtogan, something only the Big Bad Mag Mel and Drago were previously able to doing (and Mag Mel was impressed when Drago did it).
Karma Houdini: Rid a couple of Bakugan of their souls? Who cares, you’re still Mira’s brother and a good guy!
You Shall Not Pass: In Mechatanium Surge, he and Helios perform this to give the Brawlers time to escape from the impending destruction of Bakugan Interspace. He survives and makes a totally Badass comeback next episode though.
Action Girl <—> Faux Action Girl: Zigzagged. When introduced, Chan is said to be the third-highest ranked brawler in the world, but she loses all of her on-screen battles. On the other hand, however, she's shown to be quite proficient at martial arts and saves Joe from Hal-G at one point by using it.
Younger than They Look: Baron is twelve, but he's as tall, if not taller, than Ace (who's sixteen). And he's easily one of the most muscular characters in New Vestroia. Can also double as The Big Guy from the Gentle Giant perspective, since he's easily one of the largest brawlers the New Vestroia arc despite his age.
Gender Bender: Alice transforms into the male Masquerade due to being infused with some dark energy during the initial incident that severed the barrier between earth and Vestroia. Masquerade is shown to still be with her during New Vestroia, though he's unable to take over her body.
Villainous Breakdown: He doesn't take failure well. Each time his forces are defeated his motivations get more and more overboard. He goes from trying to conquer the Bakugan to trying to perform genocide on them to finally trying to destroy the whole freaking universe! Yeah, he's still pretty composed the whole time, but his motives aren't.
Took a Level in Badass: When we first see him, he is a spoiled rotten prince that waltzes around in a Not So Badass Cape, thinking he's tough stuff. When New Vestroia Arc 2 begins, he seems a lot cooler, calm and collected, plus he has the most awesome Mchanical Bakugan in the series.
Broken Faceplate: His mask gets shattered by Dan, revealing Emperor Barodius underneath it.
Chess Master: He's been pretty much one step ahead of everyone the entire season and the one time he actually lost, he still managed to come out ahead.
Cursed with Awesome: Alright, in Code Eve's defense, being imprisoned for eternity in armor made from your own evil would probably be And I Must Scream turf if Barodius hadn't found out a way to use it to feed off Chaos Energy and become even more powerful.
How does he react to getting a Psychic Link with The Hero? Not only does he use it to Mind Rape them, he uses it to take advantage of their ever growing power to absorb their energy to free him from his prison and get even stronger. He also takes advantage of the heroes being preoccupided with the chaos at Bakugan Interspace to get Team Anubias, his minions into it and start destroying it from within. And apparently a lot of Bakugan being used by people in Interspace were sleeper agents for him.
He was also smart enough to bypass the Sorting Algorithm of Evil the moment he was free and attack the Brawlers personally before they could become strong enough to be on his level. And his entire assault on Gundalia turns out to be The Plan. Winning didn't matter because he sent another group to Interspace and pretty much crippled it.
Turns out he's actually Emperor Barodius. Apparently, he's very good at learning from his past mistakes.
Hidden Villain: Nothing was known about him at first, and his true identity is only made known when Dan shatters his mask revealing he's actually Emperor Barodius.
Hoist by His Own Petard: Drago and Dan actually warned them that stolen power which wasn't their own would be their downfall. After Dan and Drago took the Gate and Key away from him and Razenoid, their stolen energy fails them, allowing Drago to kill Razenoid, Mag Mel being mortally wounded in the process.
Karmic Death: Kind of subverted. While his own actions did lead to his downfall, he and Razenoid are the only main villains to date that Dan and Drago actually killed in battle.
Knight of Cerebus: His arc is considerably more frightening than the previous villains, do in part to the simple fact that unlike the previous Big Bads, he's not after anything. He's just a murderious Omnicidal Maniac whose goal is to destroy the world. Not to mention the fact he's spent most of his arc performing a truly horrifying Mind Rape on Dan and Drago. To put this in perspective, he attacked Gundalia and began burning it to the ground.
Made of Evil: Mag Mel's armor was created by Code Eve from Barodius' evil as a means to imprison him.
Manipulative Bastard: He's pretty good at manipulating people as well, having pretty much created his two Co-Dragons to do this in Bakugan Interspace, since he was imprisoned at the time.
Mind Rape: Another thing he's been using his Psychic Link with Dan and Drago for. The worst part is, he actually seems to enjoy it!
Mook Maker: Can create Chaos Bakugan, mindless monsters existing only to destroy. He also created Anubias and Sellon.
Nothing Is Scarier: So far, there's very little known about who or what he is except he was imprisoned for genocide and is an Omnicidal Maniac seeking to destroy Earth. Arguably, this makes him even scarier than the other main villains.
In-universe, part of what makes Dan and Drago so unnerved by his is the simple fact they have no idea where he came from or what he wants with them.
Not Quite Dead: After Dan and Drago manage to unlock the power of the gate and key they have that he wants, they seeminly vaporize him but it turns out he escaped and is continuing his plot, and he now has part of Drago's gate. It turns out he was a case of this all along, as he's actually Emperor Barodius.
This would count to Emperor Barodius as well due to everyone believing he and Dharak were killed by Code Eve. They were actually imprisoned in another dimension and became Mag Mel and Razenoid.
Omnicidal Maniac: If his minions are to be believed, his goal is to destroy the world. Considering it's said he was imprisoned for genocide, this is a pretty safe bet. And the first thing he did after being unleashed was attack Gundalia with the intent of burning it to the ground. His ultimate plan is revealed to be destroying Earth to let loose a UniverseWrecking Wave that will destroy every living thing in range of it.
One-Winged Angel: Turns out he is one for Emperor Barodius and Razenoid is one to Dharak. Razenoid eventually evolves as well.
Our Dragons Are Different: Dharak, a standard quadrupedal Western style dragon which was a refreshing change of pace. Continued to be different from the others when he evolved into Phantom Dharak. Then he became Razenoid, a freaking spider legged dragon, whoopy.
Psychic Link: Drago's newest evolution resulted in him and Mag Mel being linked in this fashion. Mel is presently attempting to drain his energy to break free of his prison. He's also been using it to Mind Rape them both and later to read Dan's mind to find out what the Brawlers were planning. He eventually cuts it when Dan starts using it against him.
The Reveal: He's actually Emperor Barodius, incased in the armor of his own evil by Code Eve and imprisoned in another universe. The genocide he committed being his attempted destruction of Neathia.
Sadistic Choice: Makes the Brawlers choose between killing an innocent person and deleting his Chaos Bakugan army. Thankfully, Spectra and Dan both pull Big Damn Heroes moments to stop them from having to make the choice.
Sealed Evil in a Can: Presently imprisoned in another dimmension along with his Guardian Bakugan. Thankfully for him, he's got a Psychic Link to Drago whose got a good bit of excess power to spare. And now, he's finally free, and his first act was to launch an all out attack on Gundalia. The reason for his imprisonment is revealed to be his attempted destruction of Neathia when he was Emperor Barodius.
Taking You with Me: He tries this on Dan after being defeated in "The Final Takedown." All the energy he's absorbed is released when he's defeated and he tries to use it to take Dan and Drago down with him.
You Have Outlived Your Usefulness: To Mistress Sellon after she successfully got the Key from Dan. He "rewards" her by slowly killing her and then absorbing her energy. He even told her and Anubias that this would be their fate once they were no longer of use to him. He does it again to Anubias an episode later. It's no suprise, as he's actually Emperor Barodius!
A Nazi by Any Other Name: He and his fellows intend to perform genocide on the Bakugan to pave the way for their new Master Race of Mechtogan. As can be expected, he considers everyone else, especially Bakugan, inferior to him and the other evolved Mechtogan.
Authority Equals Asskicking: Is the leader of the four Mechtogan and the most powerful of them. And according to the game, his G-Power exceeds that of a Mechtogan Titan. And that's without turning into Mechtavius Destroyer.
Big Bad: Turns out that he and Wiseman were the same person, making him the trueBig Bad of the season.
Combining Mecha: Is able to combine with his three fellows to form the Mechtavius Destroyer. It also appears that he's the one who controls the combined form, forming the head, left arm, and core of the body.
Devour the Dragon: Does this to the Nonet Bakugan. He actually offers them the option to go willingly, but they try to fight back, only for him to kill them one by one and absorb them.
Hero Killer: Literally once he arrives on New Vestoria, he starts murdering previous heroes like they're nothing in mass. Not to mention leveling Bakugan city! Thankfully, the heroes managed to go back in time to stop him.
The Juggernaut: After going One-Winged Angel. Even Dragonoid Destroyer can't stop him and he's powerful enough to level an entire island in one strike.
What does it take to finally stop him? Dragonoid Destroyer being powered up by the energy of every Bakugan and human bond on earth that rose his power to infinite. And even then, he manages to resist it for a good time.
Villain Team-Up: Despite his hatred of Bakugan, he and his fellows are willing to work with Wiseman and his minions simply because they hate the Brawlers more. Subverted because he is Wiseman and it was all part of his plan to gain the power he needed to become completely self sustaining.
You Have Outlived Your Usefulness: The first thing we see him do is vaporize his creator now that he's evolved to the point he doesn't need him anymore. He now intends to do this to all Bakugan.
Does this to the Nonets once he doesn't need them anymore.
Well-Intentioned Extremist: Seems to honestly believe seperating the humans and Bakugan is the right thing to do. Subverted, as it turned out to be Coredegon using the Nonets to get enough power to revive himself.