That sure is an open question with many possible answers.
Maybe that he's a Montague?
Or that he killed Tybalt, her relative?
"A boy like that/Go find another/A boy like that!/Who killed your brother!" and so on.
Juliet realizes that Romeo is a Montague, her family's enemy, at the end of Act 1. She says, "My only love sprung from my only hate!" This realization sets the stage for the tragic love story that unfolds in Shakespeare's play.
He overhears her saying it when he is skulking about in her back garden.
Romeo is a Montague.
Romeo and Juliet get married.
Romeo and Juliet decide that they want to marry each other, Romeo arranges it and by the end of the act they are married.
The wedding between Romeo and Juliet occurs just after the end of Act II
they die
His wife, at the end of Act II.
The murder of Juliet's father
romeo is upset at the beginning of act one because the girl who he is in "love" with doesn't love him back. & Juliet is upset at the end of act one because she didn't know romeo was who he was at the party.
Juliet says, "Romeo, I come! This do I drink to thee!" and she drinks Friar Lawrence's potion.
Benvolio is speaking to Mercutio at the end of Act 2, Scene 1 in Romeo and Juliet. They are discussing Romeo's sudden disappearance, as he has climbed over the wall into the Capulet's garden.
Juliet's family has discovered her apparently dead and are preparing to bury her.
Friar Laurence advices moderation in love, not violent excess. Then Romeo, Juliet and Friar Laurence leave to get married.
Romeo finds Juliet asleep and assumes that she is dead. As a result, he drinks poison, killing himself. Right afterwards, Juliet awakens to find Romeo dead beside her. Overcome with grief, she takes Romeo's dagger and pierces her heart, dying in order to be with her love.