The lonely Robert Walton is delighted with Victor when he rescues him from the broken piece of ice where he has been stranded on his sledge. He writes to his sister:
My affection for my guest increases every day. He excites at once my admiration and my pity to an astonishing degree. How can I see so noble a creature destroyed by misery without feeling the most poignant grief? He is so gentle, yet so wise; his mind is so cultivated, and when he speaks, although his words are culled with the choicest art, yet they flow with rapidity and unparalleled eloquence.
Yet, as Victor's story unfolds, we can't help but perceive that he is a highly flawed character whose behavior is less than heroic. Some reasons we can't call him a hero are as follows:
He is driven too much by ambition. He oversteps human bounds and takes on the prerogatives of God when he builds his monster. Heroes are often very ambitious and "shoot for the stars," but Victor is obsessed to an unhealthy degree, cutting himself off from human society and running his health into the ground as he works night by night alone in his lab on dead body parts.
Worse, when he does create life, he flees his creation in horror, abdicating all responsibility for him. It is hard not to side with the monster when he accuses Victor of abandoning him to face a loveless and cruel world alone.
Victor exhibits a lack of sensitivity when he rips apart the bride he is building for the creature. A reader might understands his fears of creating a race of monsters, but he behaves impulsively and makes no attempt to negotiate another solution with the creature to alleviate its loneliness. He hardly seems to care or register any empathy for the creature's pain. He seems incapable of making a connection between how much he benefited from his parents' love and nurture and his own "child's" need for love.
Victor shows a high degree of self absorption and self-centeredness when he marries Elizabeth despite the creature's threats to destroy the woman Victor weds. He thinks of Elizabeth as his possession, considers the marriage from the point of view of the happiness it will bring him, and astonishingly, doesn't tell Elizabeth of the danger she faces in marrying him.
All of this behavior casts Victor in a less-than-heroic light. He might have a beautiful and eloquent exterior, but inwardly, he is fraught with problems.