Which characters are most responsible for shaping the outcome of the play? Is any one character responsible for the tragedy? Explain.

I have to go with R & J themselves. Their impulsive obsessive love drives this plot to the tragic end. There are rather misguides and headstrong characters that help but it is these two lovers that don't really think about the consequences of their actions that leads to tragedy.

Each character plays a role in the outcome. Friar Lawrence tries to manipulate things so that everyone "lives happily ever after" although he is fighting an uphill battle. Tybalt's "choler" makes him an antagonist at every turn feeling his manhood affected whenever any Capulet is around. Lord Capulet shapes the end because he feels it necessary to make Juliet marry Paris when he had said originally that she should have some more time before marrying. And certainly the impulsiveness of the two main characters shapes their destinies. Even the Nurse and Juliet's mother who basically disown her when she says she will not marry Paris play a part in the ending because Juliet no longer has anyone to confide in beyond the Friar.