Ah, Beowulf. A great hero who has probably type cast thousands of heroes after him. Honestly, the list of Anglo-Saxon hero characteristics is surprisingly similar to characteristics of modern day heroes. I teach a unit in my popular culture studies class on exactly this same topic. You could have asked about Captain America, and my answer wouldn't change much.
First, an Anglo-Saxon hero has to appear to look like a hero. What does that look like? Then, and now, hero characters are generally good looking, young, white males. They tend to have a lot of muscles, too. They have to look like a warrior. Does it apply to Beowulf? Yep. He's a young, white male that looks like a warrior. Early in the poem, Beowulf is on his way to see Hrothgar. He is stopped by a guard that demands to know his purpose. Here's one thing he says about Beowulf:
Nor have I seen
A mightier man-at-arms on this earth
Than the one standing here: unless I am mistaken,
He is truly noble. This is no mere
Hanger-on in a hero’s armour.
As for muscles, I don't have a picture of Beowulf, but he's got to be strong. Hrothgar says that Beowulf has the strength of 30 men.
"Who valuable gift-gems of the Geatmen carried
As peace-offering thither, that he thirty men’s grapple
Has in his hand, the hero-in-battle."
That's pretty strong. Oh, and don't forget that Beowulf ripped off Grendel's arms.
Another characteristic of the Anglo Saxon hero type is bravery. Yep, Beowulf has that, too. He willingly goes to fight Grendel for one, and Grendel is described as being a demon possessed thing that eats humans. No current warrior has been able to stop Grendel. That's scary, and Beowulf is confident that he will be able to handle it.
Lastly, the hero must be humble. This one always cracks me up. You have a guy that is crazy strong, brave, good looking, protects everybody, puts his life at risk, is a super celebrity, but is still humble. This is why Beowulf and Captain America are fiction. That character type is next to impossible to find in real life. So is Beowulf humble? Yep. After defeating both Grendel and Grendel's mother, Beowulf is offered the Danish throne and great wealth. Beowulf turns it all down and returns home in essentially the same state in which he arrived.
"The mildest of men and the gentlest, kindest to his people, . . ."
Beowulf resembles the traditional Anglo-Saxon hero and the more general hero of oral-traditional epic in many ways. He is skilled in the speaking of words and doing of deeds, renowned for his prowess as a warrior and evolving into a powerful and mature leader. He is also descended from a noble lineage, which is important in traditional epic.
The first trait he possesses is bodily strength and prowess at warfare. His strength is exemplified by his superhuman swimming ability. His skill in individual battle as a warrior is proven in his solitary fights with Grendel and Grendel's mother, two extremely powerful opponents.
The next important trait he demonstrates is loyalty, coming to the aid of Hrothgar, demonstrating fealty to Hygelac, and finally going out to fight the dragon to defend the Geats even though he knows that he will die in the attempt.
Finally, Beowulf learns to restrain his youthful impetuousness and pride and becomes a just and great ruler.