United Nations investigators say they have identified more than 40 South Sudanese officials and military officers who may be responsible for war crimes and crimes against humanity.
As global frustration with South Sudan's five-year old civil war grows, the report offers little hope.
Retired army colonel William John Endley was a former adviser to ex-vice-president Riek Machar, whose rebel forces have been fighting against the government of President Salva Kiir since 2013.
Across South Sudan, five years of ongoing conflict has uprooted more than four million people but peace efforts are under way both internationally and at grassroots level to end violence.
Based on the statements of 230 witnesses, it's the second report since the UN Commission was set up in 2016 to investigate human rights violations in the war-torn South Sudan.
The conflict has killed tens of thousands of people and displaced millions that have sought refuge in neighboring countries.More news: Tiffany Haddish To Host 2018 MTV Movie & TV Awards
The U.N. report details what it calls "appalling instances of cruelty against civilians who have had their eyes gouged out, their throats slit, or been castrated". Her husband was beheaded.
The court said evidence got from Endley's confiscated laptop showed he had passed on information aiding the opposition in military engagement against the South Sudan government.
The UN says the testimony gathered from survivors is "devastating", including some people being forced to rape family members "in cases reminiscent of Bosnia". It said that examining only part of this evidence had helped it identify 38 high-ranking military officers and three state governors responsible for serious rights violations and global crimes. On Friday, the Commission released its first report since it was mandated by the Human Rights Council to collect and preserve evidence for use in the Hybrid Court and other accountability mechanisms agreed under the 2015 peace agreement.
But the problem is South Sudan's government is unlikely to ever set up the court because its own military allies are thought to be some of the main culprits, reports the BBC's Will Ross.
"The Commission believes the prevalence of sexual violence against men in South Sudan is far more extensive than documented; what we see so far is likely just the tip of the iceberg", said Yasmin Sooka, chair of Human Rights Commission in South Sudan. A 2015 peace agreement collapsed and a cease-fire agreement reached past year has had little impact.