In Unforgiven,Why does the cowboy stab the woman in the beginning of the movie?
Was he crazy?
The woman is one of the younger prostitutes, working from the tavern. She upsets the cowboy by laughing at him - specifically giggling at his size.
When talking to Little Bill after the attack, Alice (the unofficial leader of the girls) says:
(from the script) - thanks Clint
Its hinted that she is less experienced than the other girls ('she didn't know no better').
It was mentioned in the film that woman had said something unflattering about the size of the cowboy's 'equipment'. This angered him and he cut her up.