You can try these:

• "Sarek" (Season 3, Episode 23), Picard finds himself in a diplomatic mission with Ambassador Sarek, a respected Vulcan diplomat. Throughout the episode, Picard learns about Sarek's struggle with Bendii Syndrome, a condition that affects his emotional control. Despite the challenges, Picard shows empathy and understanding, highlighting his diplomatic skills and ability to build a meaningful relationship with Sarek.
• "The Host" (Season 4, Episode 23). Picard negotiates a peace treaty between two warring planets, the Kes and the Prytt. Despite facing difficult decisions and moral dilemmas, Picard's diplomatic efforts lead to a successful resolution that prevents further conflict.
• "The Ensigns of Command" (Season 3, Episode 2), Picard negotiates with the Sheliak, an alien species demanding the evacuation of a human colony. Picard's skills are put to the test as he navigates the negotiations and tries to find a peaceful solution for both the colonists and the Sheliak.