When talking about the powerful heroes of Marvel. Hulk is one of the most powerful, indestructible, incredible, or immortal. His gamma irradiated anger makes him even a threat to his fellow heroes too. Therefore, thinking of a villain version of the creature might be a nightmare.
However, this nightmare happened to appear in The Incredible Hulk: Future Imperfect #1. In this, Peter David and George Perez introduced Maestro, the villain. He has the intellect as well as the ferocity of Banner and Hulk respectively. This huge, terrifying creature is one of the greatest threats to the Marvel Universe. Therefore, Hulk smashed down him to stop him from becoming the most dangerous villain.
Maestro is the Hulk of a world, who evolved from a nuclear apocalypse that recently took place there. As of result of such massive destruction, most of the superhuman of the earth were killed. Apart from making Hulk even more strongly, that apocalypse drove him insane. Also, he was mistreated by humanity, which was also one of the reasons that drove him crazy. And, now he rules that world. This made the world, even worse, with Hulk which is now being called Maestro. He tends to smash all the freedom and hope.
However, those who were not in support of Maestro ended up building a time machine. Then they used to get the Hulk into their time. As Hulk and Maestro tend to have the same intellect and power, it was not possible for Hulk to defeat him with a fight. Therefore, he tricked Maestro into following him through the time machine which took him to the time when he was actually created. Maestro then dies, there because of the explosive gamma impact.
After many years, Hulk finds out that along with finding a gamma ground zero, which created him, he was also looking for the irradiated remains of Maestro. He then made use of this in order to restore his body, which is fragile and weak. Then making the use of the Destroyer Armor against the Hulk, Maestro gets defeated. This happens when he pushes his own spirit into the armor. This forced Maestro back into his own body. His body was crushed under rocks.
He then faces a lot of nightmares to become like Maestro and he also thinks of growing his beard. After, thinking a lot Banner thought that rather than becoming a monster he should revert back to a more savage state in order to save the others.
As we know that the upcoming comic Maestro will be taking place in the world of Future Imperfect. There are chances that he could manifest within the pages of Immortal Hulk also. In this series, we see that Banner circulates constantly into many types of personalities. This will also include the so-called Devil Hulk.