The nature vs. nurture debate questions whether Frankenstein's monster was born evil, or if he learned to become evil because of his lack of "nurture".
I believe that the monster was born good and innocent. After he was "born" and left to his own devices, the monster was found watching Victor sleep. When Victor wakes, the monster smiles at him and reaches out his hand for him. These are not the actions of a violent person. The monster had the opportunity to kill or injure Victor as he slept, but he only watched his creator lovingly.
In addition, when watching the Delacey family and realizing that taking their food was harming them, he stopped taking their food and began gathering fire wood to make their lives easier. His first insticts were also to save the little girl who fell into the water, but to his surprise he was rewarded by being shot with a gun by the girl's father. These are such instances which demonstrate that the monster's "nature" is quite good.
However, the creation, who was abandoned at "birth" was left to his own devices and was never nutured. In order to be fully happy in life, everyone needs to be able to count on someone. Unfortunately, the monster never had this opportunity. He was abandoned by his own creator, beaten and chased away by villagers; he was never given the chance to fit in. When he finally has the opportunity to be "loved", by the Delacey's, Felix beats him with a stick, Safie screams and runs away, then they leave the cottage forever. The monster is then rewarded for saving a girl by being shot by her father. It is at this point that the monster utters the words "If I cannot inspire love, I will cause fear."
The "nurture" debate argues that the monster never had a chance in life. If he became a monster who killed people, it is because he had no other choice.