What is a character sketch of Yang Sun in the play The Good Woman of Setzuan?

Yang Sun is an unemployed mail pilot. He's in such despair at his lack of prospects in life that he tries to kill himself. Fortunately, Shen Te, the archetypal prostitute with a heart of gold, saves him just in the nick of time. Unfortunately, she falls in love with him.
Like just about everyone else in the play, Yang Sun proceeds to take advantage of Shen Te's kindness, and he cruelly exploits her, seeing her as nothing more than a piggy bank to be raided as and when it suits him. At no point does the selfish and manipulative Yang Sun ever reciprocate Shen Te's affections.
In due course, Yang Sun rises, socially (if not morally) to the position of factory manager. Brecht, a Marxist, uses Yang Sun as an example of how money and power can so easily corrupt the working-classes, diverting them from the path of revolution—which history has destined them to follow.