The theme of monstrosity pervades the entire novel, as the monster lies at the center of the action. Eight feet tall and hideously ugly, the monster is rejected by society. However, his monstrosity results not only from his grotesque appearance but also from the unnatural manner of his creation, which involves the secretive animation of a mix of stolen body parts and strange chemicals. He is a product not of collaborative scientific effort but of dark, supernatural workings.
The monster is only the most literal of a number of monstrous entities in the novel, including the knowledge that Victor used to create the monster. One can argue that Victor himself is a kind of monster, as his ambition, secrecy, and selfishness alienate him from human society. He is a selfish man who first creates the creature because he himself could not bear the loss of a loved one. Ordinary on the outside, he may be the true “monster” inside, as he is eventually consumed by an obsessive hatred of his creation. Finally, many critics have described the novel itself as monstrous, a stitched-together combination of different voices, texts, and tenses.
The creature that Victor Frankenstein develops is considered a monster by all of the other people. No one is there to notice that there is a soft interior underneath the hard and ugly shell. While Frankenstein would not save a life when it would have cost him almost nothing, the creature saved a life when he could have perished as well. We see that while the c!reature did murder people, he also saved others from sure death.
Essays on Frankenstein