Antagonist

"I trembled with rage and horror, resolving to wait his approach, and then close with him in mortal combat."  This was said by Victor when referring to the creature.  To Victor the antagonist would be the creature because the creature is out to get him and his family.  However, to the creature, the antagonist is Victor.  Victor is the reason for why the creature is the way he is the way he is.  Victor made the creature feel very lonely and created him looking hideous, which caused the creature to feel miserable about himself.  When so many humans rejected the creature because of the way he looked.  This caused the creature to have much hatred for humans and caused him to act out on his hatred and anger.  He began to kill Victor's family, which is why he would be considered a major enemy to Victor.