What Is Dramatically Effective about Act 3, Scene 1 of Shakespeare's "Romeo and Juliet"

By the end of act 3, scene 1 two main characters are dead and another banished, exempting them from most of the remaining part of the play. Act 3, scene 1 is a pivotal point in the play where the plot takes a turn for disaster and tragedy.
In itself this scene is bound to be dramatically effective because of the impact it has on the storyline of the play and it does not happen straightaway, anger and revenge play a large part of Tybalt's desire for a fight; but, how is the effect of the fight that eventually does happen strengthened even further onstage?
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