A United Nations diplomat recalled a closed-door meeting in which Mr. Churkin dismissed a suggestion to include women in peace talks. Get the belligerents to stop fighting instead, he said, somewhat snarkily, the diplomat recalled.

This, in turn, led Ms. Power to deliver a speech about the value of women’s leadership. Mr. Churkin yawned, the diplomat recalled, and then he walked out before she could finish.

It was often said that Mr. Churkin, a onetime child actor, leveraged his talents on the high-stakes diplomatic stage. But that does not entirely explain who he was. He had also once been a competitive speed skater. And perhaps most important, he had seen how a global superpower — his own nation — could disassemble and transform, and how its standing in the world could change.

Mr. Churkin was trained as a diplomat during the height of the Cold War, but he came into prominence as the Soviet Union was breaking apart. He was a spokesman for his Foreign Ministry in the early 1990s. He played a key role in persuading Serbs to cooperate with NATO. He served as the Russian ambassador to Belgium and Canada before his 10 years as Moscow’s envoy to the United Nations. He knew the West, and he witnessed his country’s relations with the West, specifically the United States, sink in recent years.

I was struck by how incensed he had been in early 2014 by what he considered Western meddling in Ukraine, where protests had led to the ouster of its pro-Russian president, Viktor F. Yanukovych.

He scoffed at the sight of a senior American diplomat, Victoria J. Nuland, handing out cookies to protesters. He called it a “symbol of condescension,” and derided it as “Ukrainians eating out of an American hand.”

He could also be prickly about how he came across publicly. Last fall, in an article on the military assault on Aleppo, Syria, I quoted Mr. Churkin as saying, through a Russian interpreter, that Mr. Assad had shown “enviable restraint.”