Ms. Nie tried to rescue her reputation in her later decades. She denied some of the worst accusations against her, including that she had played any role in abusing Deng’s son. But she never offered the full penitence that her critics called for. She instead dwelled on the notorious poster — a public denunciation called a “big-character poster” in Chinese political argot — that she and six other activists put up outside a restaurant on the Peking University campus.

“I accomplished just one thing in the Cultural Revolution: taking the lead in writing that big-character poster,” she said in a profile published in 2016 by the Chinese website of The New York Times. “That poster brought me tremendous fame and prominence, yet it also brought endless pain and torment for the rest of my life.”

Ms. Nie was not a typical Red Guard. When Mao began the Cultural Revolution in 1966, Ms. Nie was a midlevel Communist Party functionary at Peking University. At 45, she was more than two decades older than the high school and university students who formed the bulk of the Red Guards.

Ms. Nie was born on April 5, 1921, in rural Henan Province in central China, the youngest of seven children. Her father belonged to a long family line of well-off landowners and doctors, but many of his children embraced revolutionary politics.

Ms. Nie joined the Communist Party in 1938, in the early years of China’s war against the invading Japanese. She moved to Yan’an, where Mao had established the headquarters of the Communist forces. The wartime struggle fostered unquestioning faith in Mao and the party in Ms. Nie’s generation, Mr. Bu, the historian, said.

After the Communist Party came to power in 1949, Ms. Nie climbed the political apparatus in northeast China. Her big chance came in 1960, when she was transferred to prestigious Peking University.