Excellent movie.
And when his girlfriend tried to get back with him after she was not faithful to him, even though she wasn't with him a long time, he made a stand for humanity.
In doing so, by returning the pain back to her, she would take that lesson emotionally into her heart and hopefully change as a person for the better.
It also had a spectacular ending.
The way they played into it kept you guessing until the very end and still left it opened for your own imagination of the future.