The Hulk is already a very strong superhero, but there is someone who is more than capable of going up against him. Of course, it's basically, just another version of him.
The Maestro comes from an alternate timeline from the future. This future takes place about a hundred years after Earth as we know it, and Maestro's intelligence knows no bounds. He has become the ruler of his Earth, which he calls Dystopia, because a nuclear war eliminated all of Earth's superhumans. This allowed him to take the role he so desired.
Our own Bruce Banner has always been a gentle and humble. The Hulk, who can get out of control, has still been a hero throughout the years because he has always (or mostly) fought on the side of good. A gentle giant, basically. Maestro is their opposite--he is ruthless, manipulative, calculating and conniving.
10 HIS POWERS
For the most part, Maestro has the same powers that The Hulk has. However, because of the radiation that he has absorbed from the war that happened, he has them on a much greater scale.
His mental capabilities are a lot better, and he can interact with astral beings in a way that The Hulk was never able to do. However, he has never really shown himself to be a great technical worker in the way that Banner was.
9 AVENGERS ASSEMBLE
Although he doesn't technically appear in Avengers Assemble he is indirectly referenced. In the episode "Thanos Triumphant", Thanos goes to age Hulk into a version of himself that greatly resembles Maestro.
He does this because in the episode "The Age of Tony Stark" some future robots are brought to the present and they believed that Hulk is Maestro, which leads them to opening fire.
8 HULK AND THE AGENTS OF S.M.A.S.H
While he is first referred to as Old Man Hulk, it is actually Maestro who is in that particular present to make sure that Hulk is infected with the radiation that turns him into Maestro.
It's an incredibly detailed and long story, but at the end of it, Maestro is kept at bay, and the gamma infection is erased altogether. This saves the present and the future. Even though we basically just spoiled the ending for you, it's still definitely worth looking into the story for yourself!
7 HE CAN TRANSFORM
While the Hulk occasionally has trouble going back and forth from Bruce Banner to the Hulk, Maestro doesn't have any difficulties with it.
Maestro can transform between his human form and his Hulk form, all while retaining his true self and his mind without any difficulty. However, that doesn't mean it's a good thing. This means that Banner has given into years of darkness, essentially becoming a monster.
6 SOMEONE SURVIVES BEYOND HIM
A lot happens between the Hulk and Maestro, but something else happens on the sidelines that are quite important. Maestro got someone pregnant with a little Hulk baby.
That woman brought her son to the past in order to raise their child away from Maestro's terrible influences. Shulk, Maestro's cousin, travelled into the past in order to eliminate the child, but the plan ultimately failed.
5 IN THE FUTURE
There is no actual date, but at some point in the timeline, Maestro actually teams up with Wolverine. They go back in time in order to take down the Red Hulk.
However, they are taken down after an intense battle, in which the Wolverine of the present jumps to the future with the Hulk. They come face to face with the future Red Hulk, who informs them that in order to save the world, they have to kill the past Red Hulk.
4 THE PSYCHIC LINK
After his physical death, Maestro was able to create a telepathic link with the Hulk that he would use to his advantage (more on that below).
If Maestro had learned how to work it properly, he might have used it for more than just luring Hulk to their "birth site". He could have essentially had Hulk carry out anything he wanted, but apparently, Maestro just didn't think that far ahead. That, or, Maestro knew that everything he wanted to do would be better achieved if he was in the driver's seat.
3 THE HOMING SENSE
Ground zero, Hulk's birthplace, is actually only able to be located by the Hulk because his spirit is attracted to the remains that lay there from Maestro himself.
Maestro is able to gradually heal himself as the Hulk returns there because he is able to absorb gamma radiation through him. When he emerges, though he is feeling weak, he still tries to fight the Hulk. He fails after a battle between them with the Destroyer, and ends up being buried in a rockslide.
2 THE MEANING OF HIS NAME
While Maestro's name actually means "teacher" or "professor" his actual personality is far from that. He is nothing but a tyrant throughout his time in the comic books. Not once has he ever actually earned the term, whereas Bruce Banner, if anything, is far more worthy of it.
If any hero learns anything from the Maestro it's because they've learned something by going back and forth into the future and learning from their own mistakes, rather than directly from him.
1 A MASTER MANIPULATOR
As mentioned above, through their telepathic link, Maestro was able to lure Hulk to their birth site. That is only one example that proves that he is a master manipulator, in ways that Bruce Banner never was.
Banner was always kind and humble, but Maestro is neither. He is ruthless and experienced in years of knowledge giving him the upper hand. He often defeats Hulk because of this. Not only that, but he is able to gain followers or have people do his bidding because he is so good at manipulating them.