In Shakespeare's Romeo and Juliet, how does Nurse serve as a dramatic foil for Lord Capulet?
The best place where we can see that Nurse plays a dramatic foil to Lord Capulet is towards the end of the play. When Lord Capulet commands Juliet to marry Paris, threatening to disown her if she does not, Nurse challenges him. When Capulet calls Juliet "young baggage! disobedient wretch!" and proclaims that God has cursed them in giving them Juliet (III.v.165-172), Nurse points out that he is actually to blame for rebuking her, especially because he is forcing her to marry Paris against her will, as we see in her lines,
God in heaven bless!
You are to blame, my lord, to rate her so. (III.v.173-174)
The term "rate" can be translated as "berate," meaning "to scold" or "rebuke" (Random House Dictionary). In other words, Nurse is saying that Capulet is to blame for Juliet's behavior, not Juliet.
We also see Nurse play a dramatic foil to Lord Capulet in being the one that Juliet turns to for help and counsel, while Capulet is the one who gives commands. While Capulet does have Juliet's best interests at heart, as we see in the beginning of the play when Capulet tells Paris to wait two more years to marry Juliet and that Juliet's own consent is more important than his consent as her father, Nurse is the one that Juliet confides in (I.ii.10-11, 16-17). Nurse is the one that Juliet tells about having fallen in love with the son of the enemy. Plus, Juliet trusts Nurse enough to send her to find out if Romeo is truly making plans for marriage.