How Shylock found himself defeated in his cruel intent? What was his intent? Who was responsible for his defeat?

Just as Shylock is about to start his pound of flesh from Antonio, Portia says that the bond does not give him permission to shed Antonio's blood. The laws of Venice are such that if any Venetian's blood is shed, all the goods and lands of the perpetrator may be confiscated by the state. Shylock realizes that he cannot cut the flesh without drawing blood, and instead agrees to take the money instead. However, Portia is not willing to back down and instead only gives him the pound of flesh, further saying that if he takes a tiny bit more or less he will be put to death himself. Shylock, unable to comply with this stipulation, decides to withdraw his case.

Portia tells Shylock to remain in the court. She says that Venice has a further law which says that if any foreigner tries to kill a Venetian, the foreigner will have half of his property go to the Venetian against whom he plotted, and the state will receive the other half. In addition, the life of the foreigner will be in the hands of the Duke, who may decide to do whatever he wants to. Shylock is forced to kneel on the ground before the court, but the Duke pardons his life before he can beg for mercy.