FYI The Creature’s name is not Adam. In chapter ten, Shelly wrote,
“Remember that I am thy creature; I ought to be thy Adam, but I am rather the fallen angel, whom thou drivest from joy for no misdeed. Everywhere I see bliss, from which I alone am irrevocably excluded. I was benevolent and good; misery made me a fiend. Make me happy, and I shall again be virtuous."
The Creature first sees himself as Adam, who consciously makes the choice to sin against his creator, but The Creature did not consciously sin to become rejected by Victor. Then he states that he’s more like Lucifer, the fallen angel, because his creator abandoned him and casted him out. He was born good and innocent, seeking only love and acceptance, but over time the rejection and isolation from everywhere turned him into a devil or “monster” fervid for revenge against Victor.