Jacinda Ardern has used her final speech to New Zealand’s Parliament to describe in emotional terms how she navigated a pandemic and a mass shooting during her tumultuous five-year tenure as prime minister. She also told humorous anecdotes like how a European leader so admired the striking hair of her chief-of-staff that he fluffed it like a hairdresser — which she joked had helped secure a free-trade deal — and how her mother once sent her a uplifting message: “Remember, even Jesus had people who didn’t like him.” On a more serious note, she urged lawmakers to take the politics...