When the Security Council rejected extending the Iran arms embargo
A vote on 14 August 2020 left a US bid for an indefinite extension far short of the support it needed.

What happens when a major power asks the UN Security Council to extend an arms embargo and almost nobody agrees? On 14 August 2020, the answer was a resounding rejection of a United States bid to extend the global arms embargo on Iran indefinitely.
The United States won the backing of only one other member, the Dominican Republic. Adoption required a minimum of nine "yes" votes, so the resolution fell far short.
Eleven of the 15 members abstained, among them France, Germany and the United Kingdom. Russia and China opposed extending the ban, though the result meant they did not need to use their vetoes.
The vote belonged to a long record of international pressure on Iran. Sanctions against the country have been imposed by the United Nations and, separately, by the United States, the European Union and numerous other countries and bodies. They have been applied across successive decades in response to a range of Iranian policies, including its nuclear programme, alleged support for terrorism, human rights violations and its military conduct in the Persian Gulf.
For observers of international governance, the arithmetic of 14 August 2020 was striking: a proposal needed nine votes, received two, and was defeated without a single veto.