Maximus the Mad is the genius and insane brother of Black Bolt who often plots against the Inhuman Royal Family.
Powers and Abilities
Maximus has the ability to control the minds of others. Though psionic in nature, Maximus' ability should not be confused with telepathy. Maximus imposes his thoughts on others, subverting free will. He is able to use his mind control subtly (planting the seeds of his will in others that allow him to regain control over them after several years of cultivation) or overtly. His mind-control works on a great scale and he is able to manipulate and control many minds at the same time. However, the most dangerous thing about Maximus is not his ability to control minds, but rather his own scheming mind. He is able to come up with incredible plans and schemes that not even Karnak have been able to spot. Further he possesses superhuman intelligence and has created a vast number of highly advanced weapons and gadgets.
Hulk and the Agents of S.M.A.S.H.
Maximus secretly builds a weapon that would wipe out all human life, though it would be ineffective against the Inhumans. Only Crystal is aware of this weapon. For the majority of the episode he has the other Inhumans battle the Agents of S.M.A.S.H. He is eventually exposed and defeated, though he reactivates the barrier that shields their city from the rest of the world, but it is destroyed by Black Bolt.
He is behind the mind-control of the Inhuman Royal Family as part of his plot to have the Inhumans declare war on S.H.I.E.L.D. by dropping Attilan onto Manhattan. When Maximus tries to mind-control Spider-Man, Triton uses the Gyro-Cube to delay Maximus so that they can find Black Bolt. Upon being blasted out of the palace by Black Bolt, Spider-Man and Triton are confronted by Maximus and the brainwashed Inhuman Royal Family as Maximus prepares to drop Attilan onto Manhattan. Maximus also states that he plans to hunt all of humanity in order to make Earth an Inhuman world. Triton challenges Maximus to a battle with Spider-Man helping to fight Gorgon. As Maximus tries to mind-control Triton claiming that the humans are evil, Spider-Man knocks off Maximus' crowns freeing the Inhuman Royal Family from his mind-control. As Maximus claims that Attilan will still crush Manhattan, Spider-Man webs up Maximus' mouth to shut him up.
Guardians of the Galaxy
While having devised a cure for the Inhuman plague that had caused the Inhumans to grow crystals on their bodies, Maximus was working on mind-control technology to control Black Bolt as part of his plan to swear allegiance to the Kree. He fooled Drax the Destroyer, Rocket Raccoon, and Groot into thinking that he was the ruler of the Inhumans until Star-Lord, Gamora, Medusa, and Lockjaw arrived. Maximus then releases Black Bolt from his stasis pod and has him attack the Guardians of the Galaxy alongside the crystallized Alpha Primitives. When Ronan the Accuser arrives on Attilan, Maximus swears the Inhumans' allegiance to the Kree due to the Kree's history of having created the Inhumans. Ronan the Accuser goes back on his deal and steals Maximus' mind-control helmet to have Black Bolt teleport him and Star-Lord to the Terrigen Crystal caverns beneath Attilan. After the plague was eliminated and Ronan the Accuser was repelled, Maximus was imprisoned in the Attilan dungeon.