What does the monster say made him a fiend?

In Mary Shelley's "Frankenstein," the creature, often referred to as the monster, attributes his transformation into a fiend to the rejection and isolation he faces from humanity. He describes how the cruelty and fear of others, stemming from his grotesque appearance, lead him to embrace vengeance and violence. Ultimately, it is society's lack of compassion and acceptance that shapes him into a being filled with rage and despair.