I have always found Portia's dispensation of justice in Act Four, one of the most important turning points in the play. In Act Four, Portia stops Shylock from extracting his pound of flesh twice, after he insists upon cutting Antonio, rather than accepting payment. The second time she stops Shylock, she reminds him that the bond agreed upon by the two men did not include bloodshed, and that if Shylock insists upon his pound of flesh, all of his property and goods will be confiscated....... furthermore, if his estimations are inaccurate either more or less, Shylock will in fact lose his life.
This information stops Shylock dead in his tracks....... Shylock's initial proclamtion, "A Daniel come to judgment, yea, a Daniel!" is thus rendered a complete miscalculation. His belief that Portia had come to rule in his favor was inaccurate........ she rules in Antonio's favor.