Almost anyone familiar with the Marvel universe knows about, to some extent at least, the dynamic of Hulk vs Thor. To Hulk, Thor tends to be the one of his contemporaries amongst the Avengers that can stand in his way when enraged. To Thor, Hulk is quite possibly his greatest challenge in terms of strength and fighting ability. Now, the standard Marvel universe has Hulk winning in these contests almost every single time, but I believe there is more to this dynamic than the face value of “Hulk can defeat Thor”. What is my basis for this? Onslaught.
Onslaught is a psychic entity created when Charles Xavier attempted to permanently incapacitate Magneto, but in doing so, Xavier caused a psychic backlash which created the entity Onslaught. Onslaught has the powers of both Xavier and Magneto, incredible powers of Magnetism and psychic powers, along with telekinesis and other powers. Onslaught is, at times, a completely evil villain bent on destruction, but just trying to cause trouble at others. At one of these trouble making incidents, Onslaught wanted to find out, once and for all, who would win between Hulk and Thor. So, to find out, he mind controlled both of them and had them fight. The fight went on for a while, but Thor clearly had the upper hand. Right as Thor was about to kill the Hulk, he lost the worthiness to use Mjolnir, so Onslaught surrendered his control.
The significance of this, in my opinion, is that Thor, when going all out, is able to defeat the Hulk soundly, but he never fully attacks him, even if this is on a subconscious level, because he cannot bring himself to commit such an act. Thor’s use of Mjolnir is based on worthiness, a worthiness that can be gained and lost. At one point, for example, Captain America was granted the worthiness to wield Mjolnir. When Onslaught controlled both of the heroes, he eliminated the hesitancy that was part of Thor’s character, and when Thor moved in to finish the fight with another hero, something he would not have done under normal circumstances, he lost the ability to wield his hammer. So this creates a sort of paradox in that Thor is more powerful technically speaking while at the same time unable to go to the same lengths the Hulk could, which is how he has been shown losing to the Hulk.