He, in turn, was a master of diversion, blasting me as a self-styled “Mother Teresa” and pivoting away from Ukraine and Syria to America’s wars in Vietnam and Iraq.

Sometimes — such as when he ludicrously argued that civilians in Aleppo had simply covered themselves in dust to look like bombing victims for photographers — my abhorrence infected our working relationship.

But generally, we knew we had to work together, and we did, including byimposing the toughest sanctions in a generation on North Korea, helping mobilize a response to the Ebola epidemic and choosing a dynamic new secretary general.

Whether in monthslong negotiations or in huddles held minutes before a vote, we were able to disagree vehemently on fundamentals, but find a way to listen and discern what the other needed. Once the two of us had settled on a plan, other countries tended to defer, reasoning that if we had found common ground, so could they.

I think I learned most about Vitaly from the issues on which we failed to come to agreement. Twenty years after Bosnian Serbs murdered more than 8,000 Muslim men and boys in a clear act of genocide in Srebrenica, Britain pursued what we all thought would be a straightforward anniversary condemnation of the crime. It soon became clear that Mr. Putin, who was seeking closer ties to Serbia, was determined to prevent the Security Council from calling the killings “genocide.” Vitaly and I worked for days to come up with a version of the text that his president might allow. The morning of the vote, Vitaly couldn’t mask his disappointment when he emailed, “It didn’t fly.” He vetoed the resolution.

It is well known that it was Vitaly Churkin who raised his hand six times to veto Syria-related resolutions, but it is less known that it was Vitaly who worked frantically (and in the end futilely) to try to secure enough changes to the drafts that Moscow might support them.

Although he was the public face of so many of Mr. Putin’s harmful actions, he was also a believer in the relationship between our two countries. When Secretary of State John Kerry and Foreign Minister Sergey Lavrov tried to develop a joint counterterrorism cell in Syria, Vitaly hailed the partnership with exuberance. When the effort fell apart, he urged that we try to resuscitate it. He often told me stories from his time as an interpreter in arms control negotiations during the Cold War, drawing the lesson that, when estranged, we could start cooperating again by carving out discrete areas for progress.