By the end of the novel, Elphaba is, in many ways, truly wicked. However, we can see clearly that she is a product of her upbringing and environment and was not always the witch that she became. Her malevolence and insanity are actually quite understandable given the trauma she endures over the course of her life.

Elphaba was born as the illegitimate daughter of the Wizard of Oz and Melena Thropp. She is born with green skin, an abnormality that causes her a great deal of grief in regard to her family. Though she is a product of rape, she believes that her mother's husband Frex, a Unionist minister, is her true father.

The trauma that first poisons Elphaba's mind is her observation of and eventual obsession with the fact that Frex favors Elphaba's younger sister, Nessarose. Nessarose is almost a caricature of religious piety, the ideal daughter for the dogmatic Frex. When Elphaba and Nessarose are in college, Frex sends Nessarose a pair of ruby slippers and Elphaba nothing. The slippers become a symbol for Elphaba's inferiority complex in regard to her stepfather.

An extraordinarily traumatic series of events occurs while Elphaba is operating as a member of a resistance group against the Wizard of Oz. Fiyero, who was a schoolmate of Elphaba's, begins carrying on an affair with her. Though she warns him not to come to a location where she is operating against the wizard, he is killed by the wizard's secret police.

Elphaba, in a stupor, eventually finds Fiyero's wife and children, seeking some kind of forgiveness. Though Sarima, Fiyero's widow, allows Elphaba to stay, she will not discuss her late husband. She is eventually killed by the secret police, making the forgiveness that Elphaba desires impossible.

Elphaba loses all traces of her sanity at this point. She becomes wrathful and malevolent, lashing out at Galinda when she gives Dorothy Nessarose's slippers after her death. It is at this point that Elphaba is truly wicked, but it's plain to see that she was pushed there by the events of her life. While Elphaba is cynical, impetuous, and a bit arrogant by nature, she would have never embraced evil as she did had she been granted a kinder existence.

Although Elphaba bites people from time to time with her very prominent teeth, she does not openly torment others.  She is not given very many opportunities as a child to develop her social skills, and when she is, children shun her as do their parents because of her green skin and different appearance. 

She is protective of her sister, and aside from the ocassional nip, seems loving enough.  She is detached from others based on her experiences and treatment received from others.

At college, again she is the butt of many jokes, including, but not limited to, her roommate's vow to give her a makeover.

As with so many stories (Frankenstein, Columbine High School, etc.) she seems to have been a harmless innocent until she was subjected to endless ridicule and prejudice.  After so long, she retaliates.  We all have the potential for evil within us...