Worldwide contagion, the worst economic crisis since the Great Depression and a warming planetnot to mention rising hunger, growing legions of refugees, xenophobic bombast from strongmen leaders and a new cold war between the United States and China.
The United Nations is about to celebrate its birth in 1945 from the ruins of World War II, although "celebrate" might seem an odd choice of word amid the long list of current global woes and the organization's own challenges.
So the marking of the anniversary will be muted, and not only because world leaders will be unable to gather in person to raise a glassthe pandemic has reduced the General Assembly beginning this week to virtual meetings.
As the world body turns 75, it also faces profound questions about its own effectiveness and even its relevance.
"The UN is weaker than it should be," said Ms Mary Robinson, a previous UN high commissioner for human rights and the first woman to become president of Ireland.
When the United Nations was founded by the Allied victors, the goal was to avert another descent into another global apocalypse. And for all its shortcomings, the organization that Eleanor Roosevelt called "our greatest hope for future peace" has at least helped achieve that.
As he looked ahead toward convening this year's General Assembly, Secretary-General Antonio Guterres emphasised the long view. The values embedded in the UN Charter, he said, have prevented "the scourge of a Third World War several had feared."
Still, the organization is struggling like perhaps never before.
While it's the leading provider of humanitarian aid, and UN peacekeepers operate in more than dozen unstable areas, the United Nations has been unable to bring an end to the protracted wars in Syria, Yemen or Libya. The Israeli-Palestinian conflict is nearly as old as the United Nations itself.
UN statistics show that the number of people forcibly displaced worldwide has doubled over the past decade to 80 million. The number suffering acute hunger is expected to nearly double by year's end to more than a quarter billion, with the first famines of the coronavirus era lurking at the world's doorstep.
Mr Guterres' entreaty for a global cease-fire to help combat the coronavirus has gone largely unheeded. His plea for contributions to a US$10 billion (S$13.62 billion) emergency coronavirus response plan to help the neediest had, as of the previous week, been met with commitments totalling just a quarter of the goal.
That response "barely justifies the description of 'tepid,' " said Mr Mark Lowcock, the top UN relief official.
The United Nations, which has grown from 50 members 75 years ago to 193 members and a global staff of 44,000, was intended at its inception to provide a forum in which countries large and small believed they had a meaningful voice.
But its basic structure gives little real power to the main body, the General Assembly, and the most to the World War II victorsBritain, China, France, Russia and the United Stateswith each wielding a veto on the 15-seat Security Council as permanent members. The council is empowered to impose economic sanctions and is the only UN entity permitted to deploy military force.
No permanent member seems willing to alter the power structure. The outcome is chronic Security Council deadlocks on several issues, often pitting the United States against not only China and Russia but also against US allies.
It's not only on questions of war and cease-fires where the United Nations is struggling for results.
The Sustainable Development Goals, 17 UN objectives aimed at eliminating inequities that include poverty, gender bias and illiteracy by 2030, are imperiled.
Ms Barbara Adams, chairwoman of the Global Policy Forum, a UN monitoring group, told a conference in July that the objectives were "seriously off track" even before the pandemic, according to PassBlue, a news site that covers the United Nations.
UN veterans say multilateralismsolving problems together, a tenet of the organization's charterincreasingly collides with principles in the same charter emphasising national sovereignty and nonintervention in a country's internal affairs.
The result is often delays of aid or denial of UN access to humanitarian crises, whether in delivering supplies to displaced Syrians, investigating evidence of Rohingya massacres in Myanmar or helping sick children in Venezuela.
Professor Carrie Booth Walling, a political-science professor at Albion College and an expert on UN humanitarian interventions, said the turning inward of several countries afflicted by the virus might bode badly for the United Nations and the diplomacy it embodies.
"What is really frightening at this moment," Prof Walling said, is "the state of multilateralism in general, and whether the world's governments and people will see the value of multilateral cooperation."
The ascendance of autocratic-minded leaders has presented further challenges.
US President Donald Trump has been a frequent UN critic, rejecting notions of global governance and complaining about what he sees as wasteful spending on a budget that totals roughly US$9.5 billion annually, including US$6.5 billion for peacekeeping operations.
President Jair Bolsonaro of Brazil has called the UN's Human Rights Council a "communist meeting place." Prime Minister Viktor Orban of Hungary has railed against UN policy protecting refugees. President Rodrigo Duterte of the Philippines has expressed fury over a UN human rights inquiry into his war on drugs.
Under Mr Trump's "America First" approach, the United States intends to withdraw from the World Health Organization, with Mr Trump criticising its coronavirus response and calling it a mouthpiece for China.
Mr Trump also has abandoned or slashed support for UN agencies, including the UN Population Fund, the Human Rights Council and the agency that aids Palestinians classified as refugees.
While the United States has been lashing out, China has manoeuvred to assert more control at the United Nations, taking leadership positions in agencies that include the Department of Economic and Social Affairs, the International Telecommunications Union and the Human Rights Council.
A May 2019 study, "People's Republic of the United Nations," by the Centre for New American Security, a bipartisan research group, suggested China's UN actions were part of its effort to redefine how such institutions are run, shifting away from Western concepts of democracy and human rights.
China's UN reach extended deeper this year when Chinese candidates were chosen, over US opposition, to lead the Food and Agriculture Organization, to join a panel that chooses investigators for the Human Rights Council, and to become a judge on a UN-affiliated tribunal that adjudicates Law of the Sea disputes.
President Xi Jinping of China has exhorted subordinates "to take an active part in leading the reform of the global governance system."
The US ambassador to the United Nations, Ms Kelly Craft, has insisted she is confronting the Chinesetelling a Fox News interviewer the previous month, for example, that she raises human rights issues in China "at every opportunity we've in the Security Council."
Still, current and previous UN officials say Mr Trump's isolationist behaviour has hurt US influence at the United Nations, even as the United States remains vital as the host country and biggest single contributor.
They see an emboldened China asserting itself in contested areas of the South China Sea, suppressing dissent in Hong Kong, interning 1 million Uighur Muslims in Xinjiang, and lending aggressively to the needy countries of Asia, Africa and Latin America.
"If the United States pulls its cards out of the game, that leaves more scope for China," said Mr Edward Mortimer, who was the chief speechwriter for previous Secretary-General Kofi An. "Now China is behaving in an incredibly heavy-handed and provocative way, and has tons of countries worried."