Victor Frankenstein (Mary Shelley's Frankenstein) and Beowulf (the epic hero of Beowulf) both possess human and animalistic characteristics. For each character, the situation with which they are faced with deems that either their human character or animalistic character emerge.
The human aspects of Victor are those which one can associate with his emotional side. Linked to Elizabeth from a young age, Victor truly possesses a soft spot for her in his heart. When he comes home from Ingolstadt, to mourn with his family the loss of his brother William, Victor shows his true human nature of caring.
On the other hand, Victor does possess animalistic qualities. Like the doppelganger effect which haunts the novel, Victor's "animal" lies just below the surface of his characterization. Victor's constant desire and need to be alone proves him to be like the animal who is able to survive isolated from all others. The fact that he places his own ideas above all others illuminates the fact that he (underneath it all) believes himself to be unlike the rest of mankind.
Beowulf's human side shines with his desire to help others. A characteristics elevated by both the Anglo-Saxon culture and the epic hero, Beowulf immerses himself in challenges which aid mankind, not one which alienate him against it. At the same time, he is always (at least in the Beowulf written from the Christian perspective) acknowledging of a greater power. Upon entering into his battle with Grendel, Beowulf fails to feel any fear. While some may define this as a lack of fear, it actually exists because of his strong faith in God and God's fate.
On the other hand, one could define Beowulf's fight with Grendel as the most prominent example of his animalistic nature. Beowulf, true to the epic hero, will only fight a battle which proves honorable (the foe must be of equal or greater strength). In order to do this, Beowulf forgoes the use of any weapons in his fight against Grendel. Therefore, this sets up an epic grappling battle. Although the battle is not "shown" in great detail, one can picture the pair rolling around in battle (like two animals). Compounding this image is the fact that Beowulf literally tears Grendel's arm off--sending Grendel running off in fear.
Essentially, while each man possesses both humanistic and animalistic characteristics, each characteristic comes out for different reasons.