Which scene best describes dramatic irony from Romeo and Juliet?

Dramatic irony occurs when there is a contradiction between what a character thinks and what the audience knows to be true. Dramatic irony has been used in literature for ages. The Greek dramatists used it extensively in plays such as Antigone. Shakespeare employed dramatic irony in virtually all of his plays, especially his tragedies like Romeo and Juliet. While dramatic irony is present throughout Romeo and Juliet, it may be most evident in Act III.

In Act III, Scene 1, Romeo is challenged by Tybalt in the streets of Verona. Unknown to Tybalt or Mercutio, Romeo has just married Juliet, Tybalt's cousin. When Tybalt labels Romeo as a "villain" Romeo backs down and tells Tybalt that he actually loves him:

Tybalt, the reason that I have to love thee
Doth much excuse the appertaining rage
To such a greeting. Villain am I none.
Therefore farewell. I see thou knowest me not.

Indeed, Tybalt does not know that Romeo is now his in-law. Had Tybalt known this information, the scene may have turned out differently (or maybe not, because Tybalt was quite simply a hot head). When Romeo acquiesces without explanation, Mercutio jumps into the fray and is soon killed by Tybalt who is then killed by Romeo in a fit of revenge. Romeo is sentenced to banishment for his role in the incident. In this scene, then, dramatic irony is responsible for the deaths of two men and the banishment of another.

In Act III, Scenes 4 and 5, another example of dramatic irony occurs as Lord Capulet, who knows nothing of Romeo and Juliet's relationship, arranges a marriage between Juliet and Count Paris. When Lady Capulet introduces the idea to Juliet, who has just had her honeymoon with Romeo, she becomes distraught and argues that she doesn't want to be married. In an example of verbal irony she even says that she would rather marry Romeo, someone she hates (not really, because she already married him):

I will not marry yet, and when I do I swear
It shall be Romeo, whom you know I hate,
Rather than Paris.

Upon hearing the news that Juliet refuses to marry Paris, Lord Capulet flies into a rage and threatens to disown his daughter and throw her out into the street. The situation causes Juliet to eventually resort to drastic measures. Once again, dramatic irony disrupts and complicates the love between Romeo and Juliet.