Esther's Transformation
It would seem that the character in the megillah who experiences the biggest transformation is no other than Queen Esther. At one of the low points of her reign, she is admonished by Mordechai, "If you are silent at this desperate time, you and your family will be expunged from the annals of Jewish history." At that point, Esther, boldly calls for all of the Jewish people to fast. In essence, Mordechai has told her that her fate, and future are intertwined and interwoven with the Jewish people. Surely Esther would not have been killed by Haman, but her entire destiny, and purpose, were not mere survival, but rather, using her position to advance that of the Jewish people. Having then realized that, Esther becomes the leader par excellence - and comes full circle at a later stage when the death toll for Shushan is presented to her by Achasveirosh. Esther could have well been complacent, thanking Achashveirosh for his largesse in protecting her people. But no, Esther takes it...