The portly, wisecracking archbishop mastered the technique of criticizing Marcos and his regime but managing to pull back at the right time to ensure his continued personal and political well-being.
Those who knew him well said Sin walked a tightrope from the day he was named cardinal on May 26, 1976, until Marcos was toppled in a peaceful revolt and fled the country nearly 10 years later.
Sin was once described as "a power player who managed to turn the Catholic Church into a power center... a countervailing force against the Marcos government."
The son of an immigrant Chinese businessman and a Filipina, Sin was born in a tiny coastal village in the central province of Aklan with the unlikely name of New Washington on Aug. 31, 1928.
Apart from his local priest, Sin often said the biggest influence on his life was his mother.
A devout Catholic, she convinced her Chinese Buddhist suitor to convert to Catholicism before she consented to his proposal of marriage.
The 14th of 16 children, Sin fulfilled his mother’s wish that at least one of her children would enter the priesthood.
Ordained in April 1954 his early career as a priest was uncontroversial.
Known for his sense of humor, he often joked about his name, saying the Church would never name a "Cardinal Sin."
After becoming archbishop of Manila in 1973, he was among a handful of people that openly stood up to Marcos, who had imposed martial rule the previous year.
Sin used his pastoral letters, read during Mass, to ensure his message would be heard not only by the elite in Manila but by the masses throughout the country.
The popularity of the Church rose dramatically under Sin who was seen by the masses in this predominantly Roman Catholic country as a symbol for the resistance against the Marcos regime.
While critics branded him a "politician-priest," Sin believed the Church had an important role to play in politics.
"Politics without Christ is the greatest scourge of our nation," he said in his retirement speech in 2003.
Sin carried the fight against Marcos with courage and determination and at times with grace and humor.
The assassination of Marcos’ main political opponent, Benigno Aquino, on the tarmac at Manila airport in August 1983 was the turning point for Sin.
A close friend of Aquino, he convinced his widow Corazon, nicknamed "Cory," to run against Marcos in the snap election called for Feb. 7, 1986.
Sin then played a major role in rallying public support for the peaceful popular revolt that forced Marcos from power following the ballot, which was flawed by massive cheating.
Fearing Marcos loyalists would make one last stand, Sin was called by a friend in the US Embassy in Manila who asked: "Can you deliver the people?" To which Sin replied: "Yes, I can."
More than one million people packedthe portion of EDSA between camps Crame and Aguinaldo in Quezon City to prevent Marcos loyalists from attacking government forces who had joined the people power protest.
Marcos fled and Mrs. Aquino became the country’s first woman president.
Politically liberal, Sin remained conservative in his Catholicism, criticizing Aquino’s Protestant successor Fidel Ramos for his efforts to promote birth control.
When the next president, movie-star Joseph Estrada became embroiled in a massive corruption scandal, an ailing Sin again helped rouse the public to oust Estrada in a street uprising in 2001.
Suffering kidney ailments, Sin stepped down in 2003 and spent his time in quiet seclusion at the Archbishop’s Palace at Villa San Miguel in Mandaluyong City.
"No clergyman has had as far-reaching an effect on the political life of our country as this man from Aklan," retired Manila Bishop Teodoro Bacani wrote in 1992.
"His name will forever be associated with the ouster of Marcos, people power and the EDSA peaceful revolution," Bacani said. — AFP