Li was diagnosed with brain a tumour in June 2015 and was admitted to hospital on four separate occasions as his condition worsened, his doctors said. He had been particularly ill since January but died peacefully, his son Li Kan said.

In line with his father’s wishes, the family would not be holding a public funeral ceremony or other ritual, he said.

Sisy Chen, a political commentator and one of Li’s best friends, said she knew Li would not have wanted any fuss as he regarded death as part of the natural course of life.

“Still, I feel sad,” she said.

Li was born to his father Li Dingyi, a professor of Chinese, and mother Zhang Kuichen on April 25, 1935, in Harbin, in what was then Manchukuo, a puppet state set up by the imperial Japanese government. After leaving school, he studied history at National Taiwan University, where he quickly became known as a prolific writer, historian and sharp commentator on current affairs.

In 1972 he served four years in prison after being convicted on subversion charges for helping the pro-independence activist Peng Ming-min, who was on the run in Japan. Nine years later, he served a second, six-month, prison term for misappropriating the property of the owner of the now defunct Wenxin Magazine, which promoted democracy and political freedom. As its editor-in-chief, Li was credited with promoting Western-style democracy and calling for an end to conservatism.

After his first conviction, Li became the focus of much international attention and in 1974, while he was still behind bars, was named by Amnesty International as one of the three most important political prisoners in Taiwan.

After his release, Li continued to publish magazine and newspaper articles criticising the KMT government, and throughout the 1980s sponsored numerous anti-KMT publications. Until 1991, 96 of his books were banned in Taiwan.

Although he supported the “one country, two systems” principle and eventual unification of Taiwan and mainland China, ever since he was a high school student in Taichung, central Taiwan, Li was a fervent believer in freedom of speech.

As a teenager, Li’s teacher Yen Qiao was arrested for being a member of the Chinese Communist Party – making him a political traitor in the eyes of the KMT. Li almost found himself in prison after trying to help Yen escape, according to contemporary media reports.

“Many people chose to live with political correctness to keep things smooth,” said Chen, his best friend for 40 years. “But Li Ao always lived with his own values of correctness, which made him a person who had to constantly fight against political adversity.”

On a television talk show in 2008, Li made the bold claim that none of Taiwan’s presidents were good or capable. As well as referring to the Chiang as a dictator, he rapped Lee for “removing the words he had said during his 12-year presidency” on upholding cross-strait unity.

“What kind of leader and person is he?” Li asked, in reference to Lee’s departure from the mainland-friendly KMT to form the pro-independence Taiwan Solidarity Union.

Li also lashed out at Chen of the Democratic Progressive Party (DPP) for being a “big deceiver” who cheated voters with his promises of independence for Taiwan. “Did he actually do that? Did he dare to declare Taiwan independence?” he said.

Chen said that during the post-martial law era, many people treated Li as a “disobedient old kid”, but she considered him a man of courage, who was willing to speak out against the authorities even though he did not support Taiwan independence himself.

Because of his support for the “one country, two systems” principle and cross-strait unification – Beijing considers Taiwan a wayward province subject to eventual unification – Li was quite popular in mainland China, Chen said. For a while, at the invitation of a friend, he even hosted a political talk show on Hong-Kong-based Phoenix Television.

“But because Li often discussed the Tiananmen Square incident, he was finally forced to quit,” Chen said, referring to the mainland’s suppression of the 1989 student-led pro-democracy protests.

His refusal to compromise on such an issue exemplified his strong sense of right and wrong, she said.

While Li was a firm believer in Western-style democracy, he was never a big fan of the United States and was concerned about Taiwan’s reliance on the superpower to defend it from Beijing. American, he believed, was interested only in serving its own interests.

In 2011, he published Render America Impotent, in which he accused the US of “political priapism”. In the book, Li plays the role of god and uses various sources to put to trial 43 US presidents. In summary he describes the US as “overbearing, deceiving, and literally running on empty”.

In a news conference in 2012, Li hit out at former president Ma Ying-jeou of the KMT for trying to please the US by buying its weapons and cattle.

“What he did was tantamount to treason,” he said.

Li spent six years directly engaged in politics, and made his first run for the presidency in 2000 as a candidate for the pro-mainland New Party. His largely symbolic campaign was aimed mostly at educating voters of the importance of fighting fair and doing so without spending vast sums of money.

In 2004, he ran as an independent candidate and won a seat on the legislature, which he used mostly as a platform to berate and mock the authorities, both the ruling DPP and opposition KMT.

In October 2006, he took a dog chain and knife into a parliamentary session and questioned the motives of then Defence Minister Lee Chieh in buying American arms even after the US had treated Taiwan as a guard dog. He accused Lee of being a coward, and offered him the knife so he could cut off his testicles.

Later the same month, in a bid to end a parliamentary debate on the purchase of American submarines and Patriot anti-aircraft missiles, Li, after putting on a gas mask, sprayed tear gas and wielded a stun gun, forcing several members of the legislature to flee.

In November of the same year, he was reported to have shown a picture of himself naked as a younger man in protest against the government’s approval of a proposal to buy US arms.

Li was not only a fan of his own nude form. According to media reports, he was hugely popular with women and his home was full of naked pictures of them.

He apparently claimed to have a naked picture of Hong Kong singer Karen Mok, though she denied it, saying he had only fashion photographs of her.

At university, Li dated Wang Hsiang-chien, and though the couple never married, they had a daughter together.

On 6 May 1980, Li married former actress Terry Hu who was regarded as one of the most beautiful women in Taiwan at the time. Their romance featured in Time magazine, but the couple divorced on 28 August 1980, due to irreconcilable differences.

On 8 March 1992, Li married his second wife, Wang Chih-hui, and had a son and daughter. Their son, Li Kan, graduated from Peking University and is currently studying for a PhD in Chinese Studies at Cambridge University in Britain.

As a result of his sharp tongue, Li once said he probably had more enemies than friends.

According to local media reports, he publicly criticised more than 3,000 people and was taken to court more than 300 times, though he won most of his cases.

With his health worsening, Li wrote in June that he wanted to mend fences with those he had come into conflict, including his ex-wife Terry Hu, who later became a writer and translator.

He said he did not want to have any regrets before he died, regardless of how bloody he had fought with his enemies, or how sweet his memories of his loved ones and friends.

“Wherever you are, I would personally write a letter to invite you to Taipei, to my [home] where we can have dinner and a photo together,” he said in a public message.

Li said what he wanted most was to finish the collection of all his writings, which had been published up to volume 40, but remained far short of his goal of 85 volumes.

Li immodestly described himself as one of the top three writers in vernacular Chinese of the past 500 years.

“I have written more than 21 million words in vernacular Chinese, a lot more than the 7 million words by Lu Xuan [a leading figure of modern Chinese literature],” he said on one of his political talk shows. “And the top three writers are known as Li Ao, Li Ao and Li Ao,” he said.

Li’s writer friend Ma Kai-fai from Hong Kong said the most inspiring legacy left by Li was his willpower and bravery, that could be seen in both his personality and his work.

“Li was always clear about what to love and what to hate. He never gave up fighting for what he believed was the standard of justice in history or politics. You will seldom find a similarly strong will among contemporary Chinese writers,” Ma said.

The “sense of combative and masculine power, as well as humour” in Li’s writings immediately made Ma a fan when he first read Li’s books at the age of 17.

Ma said that in the last years of his life, Li had two major concerns. One was to finish a book titled Li Ao’s Dictionary, whose aim was to counter the “deformation and decline of the Chinese language” by telling the public the “finest and coolest ways to use a character or a word”.

The second regarded the rise of China.

“He was an old-fashioned supporter of a unified China,” Ma said. “He kept an eye on mainland-Taiwan relations. He also observed the transformation of mainland China, and was always thinking of questions, such as what strategies would be the best way forward.

“The landscape of public commentary became somewhat barren since Li was hospitalised and stopped writing,” Ma said.

“Whether you agreed with his opinions, you couldn’t find anyone who could criticise in ways as salty or witty as Li’s,” he said.

Li apparently wanted to live out his final years in Hong Kong, but was not granted permission to do so.

Ng See-yuen, a movie producer from Hong Kong, said it was a “great pity” and a “bureaucratic failure” of the city’s immigration authority not to allow Li to relocate to the city in 2012.

He told the South China Morning Post that Li wanted to move to Hong Kong because he found it “free and interesting”, so he suggested he make an application through the Quality Migrant Admission Scheme.

The scheme was launched in 2006 with the aim to “attract highly skilled or talented persons to settle in Hong Kong”. Successful applicants included pianists Li Yundi and Lang Lang, and actresses Zhang Ziyi and Tang Wei.

“I sent my recommendation for him to the Immigration Department,” the 74-year-old Ng said. “But the officers asked him for proof of his achievements, and an explanation of his imprisonment. All these bureaucratic failures irritated Li and drained his interest in pushing the application forward,” he said.

“If the immigration officers didn’t know how many books Li had written, and that he was a political prisoner, that would be a lack of general knowledge and obvious imbecility,” he said.

Despite being his friend for 30 years, Ng said Li’s shortcoming was that he was “relatively radical”.

“If you were in a bad relationship with him, your days were tough, because he would dig up every single bad thing you had ever done,” he said “But if you were his friend, he would always stand by you and speak up for you.”

News of Li’s death started a massive outpouring of grief online. As of 5pm Sunday, the topic #Li Ao passed away had attracted 100 million views and 70,000 comments on Weibo, China’s Twitter-like service.

Thousands more fans left their condolences on Li’s official Weibo page.

Ma Wei-du, an antiques collector and founder of the Guanfu Museum in Beijing, wrote on Weibo: “Mister [Li] was a chivalrous and plain-spoken person, which made him a fellow maverick in Chinese literati.”