As far as I can see it, Friar Lawrence has a huge responsibility regarding Romeo and Juliet's death. Even though his intentions are extremely worthy, such as to marry the couple and thus unite the rival families, his plan to pretend Juliet's mortality is enormously dangerous. Not only Paris and Romeo died for her at her tomb, but also her family could have taken a drastic decision after her passing over. Furthermore, he was too slow to tell Romeo beforehand about Juliet's potion, acknowledging Romeo's deep love and obsession for Juliet. Finally, Friar Lawrence is acquainted with Juliet's suicidal tendencies, so he should have been particularly careful when designing a plan to help the couple.