The world’s fault lines have turned from cracks into canyons as superpowers show that they alone do not have the military, economic and technological power to guarantee security or solve the world’s problems, the outgoing secretary general of the United Nations has said in his final address to the general assembly.

In a speech laced with despair but also glimpses of defiant hope, António Guterres said that over the last decade, largely spanning his 10-year period in office, “wars erupted with devastating consequences and dragged on with despicable cruelty. Civilians were targeted. Human rights trampled. Hunger weaponised. Humanitarians killed. International law cast aside.”

He continued: “Geopolitical divides have deepened. Inequalities have intensified. Trust has frayed. The climate crisis went from distant warning to daily reality. And artificial intelligence moved at a speed that has blindsided even those who created it.”

Without naming Israel, he said what followed the Hamas attack of October2023 “was an onslaught on Palestinians in Gaza, with a scale of killing and destruction unlike anything I have witnessed in all my years as secretary general”.

He rounded on profiteering energy companies for “treating the world as an open sewer”, described Africa’s omission from a permanent place on the UN security council as stunning, and called for a new compact to regulate AI.

Throughout, the 77-year-old Portuguese politician and diplomat argued that a multilateral system centred on a newly representative UN was the only way to address this new convergence of problems. However, he warned: “At the very moment when humanity faces an unprecedented convergence of threats, our mechanisms for collective action are under growing strain.”

Without mentioning Donald Trump once, he said what was required was “a recognition, especially by superpowers, that their power isn’t so super. Their power has limits. The events of recent years have made that unmistakably clear. Military power alone cannot secure peace. Economic power alone cannot command stability. And technological power alone cannot guarantee security.”

It was critical to avoid hegemonic tendencies and what Guterres described as the “great fracture” – the division of the world into two rival blocs with separate economic, technological and security systems.

The defining challenge of the age, he said, was that world governance, reflecting the power realities of a bygone age, was not adapting to the way power was being redistributed between and within states.

At the same time there was “an extraordinary transfer of power away from governments to a handful of private corporations and individuals. Their reach now extends across politics, economies, information flows, technological development, and the civic space on which societies depend,” he said. “Humans are increasingly handing over power to machines – with artificial intelligence agents going rogue, and lethal autonomous weapons going from science fiction to military reality.”

The choice was now whether the world was going to continue to fragment with rising tension, transactionalism and shrinking cooperation or change course towards a multilateral system centred on a UN that was balanced and representative. “The test before us is whether power will be exercised with the law – or beyond it,” Guterres said. “We must pass that test. We must defend the charter without double standards. Protect civilians without exception.”

He urged world leaders to stop letting civilians pay the price for the cascading conflicts across the Middle East. Demanding that the fighting must stop and humanitarian aid must flow, he pointed out that the international court of justice had ordered last year that the UN be allowed to fulfil its mandates in Gaza.

“Meanwhile violence, displacement and settlement expansion in the occupied West Bank are bulldozing the path to peace and raising the spectre of ethnic cleansing. We cannot allow the two-state solution to disappear before our eyes,” he said.

In Ukraine, Guterres said, “Russia’s full-scale invasion has subjected a sovereign country to a brutal war in blatant violation of the charter”. But now, he also warned, “in parts of Russia homes, energy and water systems and transport have come under repeated attack, threatening food and energy supply chains globally”.

For decades, he said, “big oil has treated the atmosphere as an open sewer – and cashed in on the consequences. Since Russia’s invasion of Ukraine, five major western oil companies have pocketed nearly half a trillion dollars in profits. Compare that with just $34bn in international public adaptation finance for developing countries in the latest year reported.”

He added: “With a supersized El Niño coming towards humanity, everyday people are paying more for energy, food and insurance.”

Although he admitted a 21st-century security council without permanent African representation was unjust and indefensible, he defended the cash-strapped and much maligned organisation, saying the UN was where the powerful were held to account.

He announced that the United Nations had “achieved gender parity for the first time in history across all senior leadership … all headquarters … and all professional staff”.

“Equality is not a dream. It is a decision,” he said. “If the UN can change, so can businesses, parliaments, governments, peace processes.”