Charlize Theron. She was the one who took on the challenging role of the main character in 'Monster 2003'. Theron really immersed herself in the role of Aileen Wuornos. She not only changed her appearance but also managed to convey the character's emotions and motives very effectively. Her performance was one of the key factors that made the movie so impactful, as it was based on a true story and she made the character seem very real.
The main character in the movie 'Monster 2003' was played by Charlize Theron. She completely transformed herself for the role. She captured the essence of Aileen Wuornos, from her rough exterior to her complex inner turmoil. It was a remarkable performance that brought the real - life story to the big screen in a very powerful way.