Final answer:
In 'Frankenstein' by Mary Shelley, DeLacey, Agatha, and Felix were betrayed by the monster, as a result of its desire for revenge against its creator for the rejection and mistreatment it faced from humanity.
Step-by-step explanation:
In the novel Frankenstein by Mary Shelley, the characters DeLacey, Agatha, and Felix were betrayed by the monster, also known as Frankenstein’s creation. After the creature learns about human nature and becomes more conscious of his own existence, he longs for companionship and acceptance. Despite attempts to integrate into the DeLacey family's life, the monster is ultimately rejected and mistreated. Feeling betrayed by humanity, the creature seeks revenge on his creator, Victor Frankenstein, which indirectly leads to hardships for DeLacey, Agatha, and Felix.