The viewpoints and personalities of the characters in Frankenstein tend to illustrate different aspects of Mary Shelley's main themes, which include ambition and the importance of family.
The characters who most epitomize the themes of ambition are Victor and Walton. Victor's pursuit of knowledge and power leads to not only his early death, but the extermination of everyone he loves. In spite of this, he does not appear to regret his decisions entirely. When Walton is tempted to quit his hopeless expedition to the North Pole, Frankenstein urges Walton and his crew to be "more than men"—that is, to risk everything for ambition. However, Walton takes the opposite course, returning home to his family.
Family is another major theme the characters develop through their lives and actions, primarily the companionship having a family brings the individual. Frankenstein appears to take his family for granted, while the creature craves a family desperately. The closest the creature gets to experiencing familial love is when he spies on the De Lacey family, and even then, he is only able to experience it secondhand. When he tries integrating himself with them, he is rejected.
The creature's desire for family motivates him to seek out Frankenstein to make him a mate, but when this desire is also rejected, he takes out his revenge on Frankenstein's family, killing them one by one. As the creature tells his creator, "If I cannot inspire love, I will cause fear," suggesting that tyrannical power is his only alternative to being loved. Once Frankenstein is also left alone in the world, he becomes twisted with rage and the desire for vengeance, suggesting that people need companionship in order to be mentally healthy.