At least 30 countries illegally forced refugees to return to places where they would be in danger last year, Amnesty says as it warned that many governments were brazenly breaking international law.
War crimes or other violations of the "laws of war" were committed by governments or armed groups in at least 19 countries, Amnesty said in its annual review of human rights around the world published on Wednesday (local time).
Amnesty Secretary-General Salil Shetty said short-term national self-interest and draconian security crackdowns had led to an "unprecedented assault on human rights" in 2015.
"Your rights are in jeopardy: they are being treated with utter contempt by many governments around the world," he said.
One of the most egregious examples of countries turning their backs on asylum seekers took place when human traffickers left thousands of people from Myanmar and Bangladesh adrift on the open seas without food and water.
Hundreds are thought to have died from thirst and hunger as countries in the region played "ping-pong in the sea" with them, Amnesty said.
In Europe, the report strongly criticised Hungary for sealing its borders to keep out thousands of desperate refugees and obstructing collective regional attempts to help them.
More than a million refugees and migrants arrived in Europe last year, many fleeing war zones. Amnesty said that with the exception of Germany, the response to the crisis had been woeful.
"That Europe, which is the richest bloc in the world, is not able to take care of the basic rights of some of the most persecuted people in the world is shameful," Shetty said.
He called for the world to find legal and dignified ways for refugees to reach safety and said 1.2 million of them must be resettled without delay.
Around half the arrivals in Europe last year were from Syria, which Shetty described as a "human rights-free zone".
Amnesty condemned the killing in Syria of thousands of civilians in direct and indiscriminate attacks with barrel bombs and other weaponry, and criticised lengthy sieges of civilian areas and the blocking of international aid to starving people.
It also said Saudi Arabia had committed war crimes in the bombing campaign it had led in Yemen and criticised it for obstructing the establishment of a UN-led inquiry into violations by all sides in the conflict.
Shetty warned that not only human rights, but also the laws and institutions meant to protect them, were under attack.
Many African countries have threatened to walk out of the International Criminal Court, which was set up to end impunity for leaders who commit war crimes.
Countries hampering co-operation with the ICC include Kenya, Ivory Coast and South Africa, which ignored a court order last year to arrest Sudan's president.
Shetty also said too many governments were using the threat of violence from armed groups as an excuse to "take short cuts on human rights".
"The human rights of civilians cannot be sacrificed under some vague notions of combating terrorism," he said.
"Human rights are a necessity, not an accessory [...] the stakes for humankind have never been higher."
Amnesty's annual review, which includes reports from 160 countries and territories, said there had been some gains for human rights last year.
Three countries -- Madagascar, Fiji and Suriname -- abolished the death penalty in 2015, and Mongolia is set to do so in 2016.
Other countries launched national campaigns to end child marriage or passed laws to recognise same-sex relationships.
Facts and figures from Amnesty International report: