You could approach this topic from a couple of angles. First, the monster longs for recognition simply as a living creature. From the moment he is created and comes to life, Frankenstein rejects him and fairly tries to pretend that he doesn't exist. Pushed to the edges of society and met with scorn from every human he encounters, the monster's lack of any form of even neutral recognition pushes him to lash out and kill his creator's younger brother. Because his creator fails to recognize his existence and because other humans (such as young William) recognize his existence only in fear and disgust, the monster's sense of violence and retribution grows.

You could also examine the monster's interactions specifically with the DeLacey family. The monster anonymously reaches out to help this family by cutting wood for them and by foraging for himself instead of stealing from their meager rations. During this time, the monster's intelligence grows rapidly, and he believes that this kind and warm family could finally offer the positive recognition he longs for. However, when his true physical appearance is revealed and they recognize the creature only for his physical deformities, they try to attack him. He is rejected yet again, denied the recognition not only being a fellow living being but also denied the recognition of all the ways he's helped the family throughout the preceding weeks.

The need for acceptance, even within a small group of people, is one of the most fundamental human needs. People need to feel that they have a safe spot to land and a group of people who will accept them no matter their shortcomings and mistakes. If people were only met with violence in their efforts to gain this recognition, it would fundamentally change the nature of their personalities. People who are constantly met with violence and anger are more likely to become violent and angry. Consider the cycle of child abuse. Why do children who are abused often grow up to be child abusers themselves? Not only is it a learned pattern of response, but it often also changes the way these people perceive the world around them. Humanity becomes fearsome, untrustworthy, and harsh. The monster demonstrates this same principle; because his efforts for acceptance are constantly met with fear and anger, his personality becomes hardened and bent on revenge toward the world that fails to recognize his inner strengths despite his outward appearance.