Final answer:
Samuel Pepys thought 'A Midsummer Night's Dream' was the worst play he had ever seen, as recorded in his diary entry from September 29, 1662.
Step-by-step explanation:
The play that Samuel Pepys, the famous English diarist, thought was the worst he had seen is A Midsummer Night's Dream. This is somewhat ironic, as today it is considered one of Shakespeare's most beloved works. Pepys saw the play on September 29, 1662, and his diary entry on that date reflects his disapproval. Pepys, known for his candid and personal reflections on the many plays he attended, gave no quarter in expressing his distaste for this particular production, despite the play's standing now as a staple of classic theatre and its frequent study in educational settings.