The Incredible Hulk is often referred to as "The Strongest There Is," and for good reason--at his very strongest, his footsteps aren't just lethal, they're literally seismic.
While the Hulk has taken many identities over the years, aside from his regular Hulk persona, none can compare to the "Green Scar" persona. Originally debuting in the "Planet Hulk" storyline, the Green Scar persona emerged after accidentally being sent to the Planet Sakaar, an attempt by the Illuminati to rid the earth of the Hulk. In a short period of time, the Green Goliath went from being enslaved to eventually ruling the entire planet, having found a wife, friends, and a kingdom to rule. But his peace would be short lived, as a bomb planted in Hulk's ship blew up his entire kingdom, along with his wife. With his Warbound allies at his side, Hulk could only think of one thing: revenge!
Hulk had believed that Earth's heroes had planted the bomb on his ship in an effort to kill him in space, rather than send him away. Thus, Hulk and his allies would make their way to earth in the World War Hulk storyline, to exact their revenge on those who harmed them. The timely intervention of The Sentry, an extremely powerful hero and Hulk's longtime friend, would cease the bloodshed, as both combatants at full power managed to wear each other down. Though it seemed as though war was over, with Hulk reverting to his Bruce Banner form, things would only get worse.
At the apex of his anger, the Hulk began trembling with rage, emitting energy so powerful, that even as he walked, New York City began to crumble. Even in Connecticut and Massachusetts, the residents there would feel trembling and witness the oceans rising, with military personnel informing the President that, if the Hulk would take another few steps, the Eastern Seaboard would be annihilated. The Hulk was still enraged at the Marvel Heroes, as it was still because of their actions that the Hulk found love and lost it once again. Though it seemed like the world was about to literally break, Iron Man had a contingency in place.
Though the Green Scar personality has occasionally returned over the years, its powers are undeniably great. Green Scar was able to go toe-to-toe with Sentry, Marvel's equivalent of Superman, and wear him down, while the Banner personality was still standing. At his angriest, Green Scar was emitting energy so fierce, that the rest of the world could feel it, and if even his footsteps can cause streets and buildings to break easily, it would be almost scary to think what would happen if he threw a punch in that state. In some instances where Green Scar was about to surface, such as Hulk fighting his son, Skaar, Hulk and Banner would almost immediately suppress the identity, as if even Hulk himself was scared of Green Scar's destructive powers. Needless to say, if Green Scar would reemerge for a long time, it should worry any enemy of the Hulk, and they definitely would not want to make him angry.