When Romeo kills Tybalt, he increases the friction with Juliet’s family.
Before the deaths of Mercutio and Tybalt, the families were in a long feud that had only been kept up by small skirmishes. When Mercutio and Tybalt are killed the feud has a renewed strength. The Capulets are calling for the Prince to kill Romeo as punishment. Juliet even struggles with what to do because on the one hand she thinks she should hate Tybalt's killer, but on the other hand she loves Romeo. She eventually decides that she can forgive Romeo for her cousin's death because if he hadn't killed Tybalt, Tybalt surely would've killed him. The rest of the options are simply incorrect. Romeo's friends are not impressed, the prince is not grateful, and Romeo is not notably injured.
