It is not an exaggeration to say that it is necessary for these heroes to have superhuman strength. They both live in a world where great power is needed to oppose evil. For Beowulf, who lives in a warrior society where monsters freely roam, terrorizing the common people and for Spiderman, who needs the strength to protect the innocence from powerful nemeses. It is because there is a need for their power that they have access to it, and use it in the way we expect. .
With the great need for them in the hero's respective society, superhuman strength is one of the most important building blocks for establishing both Beowulf and Spiderman as heroes. A line from the first Spiderman captures his rather well. "With great power, comes great responsibility" says Uncle Ben, referring to Peter (Raimi 2002). In this context, Beowulf, who possesses strength like no other man, has a responsibility to defeat the raging Grendel monsters who threaten his society. Should he not use his power to defeat evil, Beowulf would be no more than a villain. The same thing could also be said about Spiderman. When he first obtains his power, he simply uses it for his own needs. One could not call Peter a hero at this point; he has yet to fulfill his heroic responsibilities. Moreover, heroes are given superpower because they have villains, whose power is equal to or perhaps greater than the hero. As assessed by Kathryn Hume, in her article: Saga to Romance: The Use of Monsters in Old Norse Literature, "The monster preys upon society, thus letting the hero put his strength to the service of others" (Hume 3). She also provides other poems that follow the same convention of heroes fighting monsters/villains, including Beowulf, despite it having an Anglo Saxon origin. Her article also conveys one's point that heroes exist because there is a need for them. On the other hand, Sir Gawain possesses no superhuman strength despite his valor in other works.