Romeo Montague
Romeo is impulsive, emotional, and fast to act on feeling. He moves from obsession with Rosaline to total devotion to Juliet in one evening. His best quality is his capacity for love. His worst is that he acts before he thinks, which is exactly what kills him at the tomb.
Juliet Capulet
Juliet starts the play as an obedient thirteen-year-old and ends it as someone who defies her family, fakes her death, and chooses to die rather than live without Romeo. She's more practical than Romeo and often more clear-headed. Her tragedy is that she has no trustworthy adult to help her.
Friar Lawrence
Friar Lawrence marries the couple, devises the potion plan, and then fails to make sure the plan actually works. He means well at every step. His good intentions and poor execution make him one of the most consequential characters in the play. He's not a villain, but he's not blameless either.
Mercutio
Mercutio is Romeo's closest friend and the play's most energetic voice. He's witty, cynical about love, and loyal to Romeo. His death in Act 3 is the moment the play shifts from romantic comedy to tragedy. He blames both families as he dies.
Tybalt
Tybalt is Juliet's cousin and the Capulet family's enforcer. He hates Montagues on principle and picks fights whenever he can. His challenge to Romeo sets off the chain of events that leads to banishment and death. He's not complex, but he's effective as a plot engine.
The Nurse
The Nurse raised Juliet and is her closest confidant for most of the play. She helps arrange the secret marriage. But when things get dangerous, she tells Juliet to just marry Paris and forget Romeo. That betrayal leaves Juliet completely alone in Act 3 and forces her toward Friar Lawrence's desperate plan.
Lord Capulet
Lord Capulet starts the play as a relatively reasonable father who says Juliet should have some say in her marriage. By Act 3, he's threatening to throw her out if she refuses Paris. His shift from lenient to controlling traps Juliet and removes her last legitimate option.
Prince Escalus
The Prince represents civic authority in Verona. He warns both families at the start, then banishes Romeo instead of executing him after Tybalt's death. His decisions shape the plot, but he's largely reactive. At the end, he admits the city shares blame for what happened.