A tragic flaw is the flaw that brings about the downfall of the tragic hero. Aristotle suggested that the tragic hero is doomed by forces mostly out of his control. The most important point is that the hero is otherwise noble, and the tragic flaw is his downfall.
Romeo and Juliet share a flaw: overreliance on passion rather than common sense. In other words, they act without thinking. All they care about is how much they want each other, and they don’t really worry about the consequences.
In Romeo and Juliet’s case, they tend to bring out the downfall of each other. For example, when Juliet tells Romeo her family will kill him if they see him, he responds:
I have night's cloak to hide me from their eyes;
And but thou love me, let them find me here.(80)
My life were better ended by their hate
Than death prorogued, wanting of thy love. (Act II, Scene 2)
Romeo tells her that no one will see him, and he’d rather die than not spend time with her.
A tragic flaw in literature refers to a shortcoming in a character's nature which leads to his or her downfall. The Greek term for this is hamartia, and it is a literary technique used by writers in a drama to teach the audience a moral lesson. The audience can then learn from the mistakes committed by the character(s) and avoid doing the same.
Romeo and Juliet's primary character flaw is their lack of judgment. They were both unable or unwilling to carefully consider their actions and those actions' outcomes because they were ruled by passion and, therefore, acted on impulse. Their impetuous acts lead to their tragic end.
Throughout the play, there are a number of examples which illustrate this aspect. After they first meet and fall for each other, Romeo and Juliet meet secretly, knowing full well that they are taking a huge risk since their families are enemies. The two should have realized that their relationship was doomed to fail and should have considered other methods to improve its chances of success. They foolishly indulged their passion, however, and dragged others, such as friar Lawrence and the nurse, into their affair.
Their awareness of the risk did not deter the two lovers, as is evident in the following excerpt from Act l, Scene 5:
Is she a Capulet?
O dear account! my life is my foe's debt.
My only love sprung from my only hate!
Too early seen unknown, and known too late!
Prodigious birth of love it is to me,
That I must love a loathed enemy.
Another example would be Romeo's foolhardy desire for revenge. Once Tybalt kills Mercutio, Romeo is intent on exacting revenge against his enemy, and goes about doing just that. He kills Tybalt and is banished for life. His actions bring about a dramatic turning point in the play, adding another layer to an already complicated situation.
Juliet's fervent and passionate resistance to her parents' desire that she should marry Paris is admirable, but her recalcitrance, one surmises, could have been better managed if she carefully considered her situation and approached the issue more rationally.
The two lovers' quick decision to get married is another example of their lack of forethought. Friar Lawrence's urgings, in this regard, should merited deeper consideration. The lovers were so driven by their desire to be together that they eagerly consented to his suggestion.
There are many other examples of the two lovers' lack of judgment in the play. One of the most pertinent is the fact that Juliet had agreed with friar Lawrence on a desperate measure to trick her parents into believing she had died. This action, more than any other, would directly lead to her and her lover's deaths. The lack of proper planning, in this regard, eventually results in the two committing suicide.
In the final analysis, then, Romeo and Juliet pay the ultimate price for their indiscretion and leave behind the broken pieces their families would attempt to piece together. Fortunately, their deaths brought an end to the families' malicious feud.
Their flaw is their impulsiveness. The entire story happens over the course of a few days. Romeo kills himself after he sees Juliet "dead". If he had waited, there would have been no need as she was, obviously not dead.