Romeo and Juliet
The fault for Romeo and Juliet's death is no one else but Romeo himself. He brought his irresponsibility and impulsiveness amongst himself.
When Romeo sees Juliet at the Capulet's household he falls deeply in love with Juliet. The thing is that there is no such thing as love at first sight. You can fall in love with the semblance appearance, but that's not every thing. Looks help but what counts is what's in the inside. Romeo is too young to know what true love really is.
Romeo then goes wandering around in the Capulet's orchard looking for Juliet. He sees her on the balcony and the two start confessing their love for each other. With Romeo sweet-talking Juliet, he convinces her to marry him the next day. He doesn't know what he is getting himself into, Juliet is a Capulet and Romeo is a Montague.
The family feud would never except the two getting married. The resolution Juliet has to solve this problem is to feign her death. That just caused a lot of chaos and confusion. Which made Romeo kill himself and Juliet to stab herself. So now the two are both dead because Romeo was very irresponsible.
Romeo can be impulsive like when Tybalt was being belligerence and wanted to challenge Romeo to fight, but he backs out. Instead Mercutio wanted to fight Tybalt. Romeo tries to stop them, but Tybalt stabs Mercutio and kills him. Romeo doesn't know how to react. With out even thinking about what would happen to him, he kills Tybalt. Now Romeo is banished from Verona. If he comes back he will be executed. Romeo does things with out even thinking first.
With Romeo being irresponsible and impulsive none of them would have died. Romeo falls...