romeo kills him
Mercutio steps in and fights Tybalt instead.
Tybalt wants to start a fight with Prince Paris Hoe!
Romeo kills Tybalt in Act III, after Tybalt has killed Mercutio in a duel.
It's in Act III Scene 1, somewhere around line 130, depending on your edition.
Act III, Scene 1 is the climax because there is no turning back for Romeo after he kills Tybalt.
[You meant ''Who is Tybalt?''] Tybalt was Juliet's cousin. He is a Capulet. He kills Mercutio and soon dies by Romeo. Then Juliet gets mad at Romeo for killing her cousin (The Nurse tells Juliet that Romeo killed Tybalt). Soon Juliet forgives him because she cares more about Romeo banish (He got banish because he killed Tybalt, Friar Lawrence gives him this news) than Tybalt's death.
In Act III, Scene 1, Mercutio was the first one to mention fighting. Eventually, Tybalt stabs Mercutio.
Tybalt's father is Mrs. Capulet's brother. She says so in Act III Scene 1: "O my brother's child!" Who his mother is we are not told.
In Act III of Romeo and Juliet, a series of tragic events unfolds. Romeo kills Tybalt in a fit of anger, which leads to his banishment from Verona. Juliet is heartbroken by the news of Tybalt's death and Romeo's banishment. To avoid marrying Paris, Juliet seeks help from Friar Laurence, who devises a plan for her to fake her death with a sleeping potion.
Romeo fights Tybalt in Act 3 of William Shakespeare's play "Romeo and Juliet." Tybalt is Juliet's cousin and a skilled swordsman, leading to a tragic confrontation that results in Tybalt's death.
Mercutio and Benvolio trade insults with Tybalt. Romeo arrives, but refuses to quarrel with Tybalt (who is now his cousin by his secret marriage to Juliet). Mercutio is willing to fight, but is killed by Tybalt as Romeo tries to intervene. Romeo, enraged, pursues and kills Tybalt. Prince Escalus banishes Romeo.
Tybalt wants to fight him. Tybalt always wants to fight someone, and he has fastened on Romeo after Tybalt spotted him at the party in Act I Scene 5.