Yoon Suk-yeol has undergone a dramatic transformation from a prosecutor general serving President Moon Jae-in to an opposition presidential contender vowing to investigate the administration's "deep-rooted evils" if elected on March 9.

Yoon, 61, rose to prominence as a prosecutor investigating high-profile cases under the previous conservative administration of President Park Geun-hye, including the massive corruption scandal that led to her impeachment and imprisonment.

His status earned him the position of prosecutor general under Moon, but he soon fell out of favor with the liberal administration for targeting his investigations at the president's inner circle.

As public discontent with the Moon administration grew, Yoon faced calls to run for president as the candidate of the main opposition People Power Party (PPP), and with only a year left until the election, Yoon left the prosecution last March and launched his presidential campaign on the conservative party's ticket.

Yoon's role in the investigation into former President Park was a source of consternation for some conservatives, as she held a special place in their hearts as a daughter of the assassinated former President Park Chung-hee.

But Yoon's boldness in the face of power, and his steadfast adherence to principles, gave rise to hope that a Yoon presidency could meet their demands for justice and the rule of law.

Born to parents who taught at universities, Yoon studied law at Seoul National University after following the advice of his father who encouraged him to study law even though he had a strong interest in economics.

Shortly before Chun Doo-hwan, the country's de facto leader at the time, ordered a bloody crackdown on a democracy uprising in Gwangju in May 1980, Yoon took part in a mock trial at his university and sentenced Chun to life imprisonment.

To escape retribution, Yoon fled to the eastern coastal town of Gangneung where his mother's side of the family lived and stayed there for three months.

In 1991, Yoon passed the bar on his ninth try.

"This administration is probably very afraid and sick to the bone about my victory in the primary," Yoon said in his acceptance speech after winning the PPP's nomination in November.

"That's because I am the symbol of fairness who toppled Cho Kuk's hypocrisy and Choo Mi-ae's arrogance, as well as the fatal pain that destroys the legitimacy of the Moon Jae-in administration," he said.

Cho served briefly as justice minister under Moon before an academic fraud scandal involving his family forced him to resign. Choo was appointed to succeed Cho and clashed repeatedly with Yoon while aggressively pushing the president's agenda for prosecution reform.

The animosity between Yoon and Moon resurfaced in February when the candidate told a local newspaper he would launch an investigation into the administration's "deep-rooted evils" if elected, and the president slammed him for making "groundless" allegations.

During the course of his campaign, Yoon made a series of controversial pledges that appeared to target conservatives and young male voters in their 20s and 30s.

On North Korea, he suggested the need to launch a preemptive strike in the event of an imminent threat from the regime and pledged to deploy additional units of the US THAAD antimissile system in South Korea to deter North Korean aggression.

On relations with the United States, Yoon called for deepening the bilateral alliance as the central axis of Seoul's foreign policy, while on China, he vowed to further upgrade the two countries' relationship despite noting that most South Koreans do not like the neighboring country.

With Japan, Yoon vowed to repair the deeply fractured relationship by recognizing the suffering of South Koreans under Tokyo's 1910-45 colonial rule but also looking to a future of co-existence.

Yoon prompted criticism after pledging to abolish the Ministry of Gender Equality and Family, which his opponents viewed as a move to woo young male voters resentful of the rise of feminism.

The COVID-19 pandemic was a recurring theme during the race.

To help small businesses hit by the government's tough virus restrictions, Yoon promised to provide 50 trillion won ($41 billion) in loans and another 43 trillion won in cash handouts.

In the real estate sector, he pledged to supply 2.5 million new homes and help stabilize home prices by easing regulations and lowering capital gains and property ownership taxes.

Yoon frequently came under attack for his careless remarks, such as when he praised the political leadership of Chun, with the exception of his staging of a military coup and his crackdown on the 1980 uprising.

The candidate was accused of relying on superstition and shamans after he displayed the Chinese character for "king" on his palm and was reported to have ties to an anal acupuncture specialist.

The biggest liability for Yoon was his wife, Kim Keon-hee, who was accused of taking bribes and manipulating stocks before he launched his campaign and later faced allegations of lying on her resume when applying for jobs.

The couple married in 2012 and live with four dogs and three cats. They have no children. (Yonhap)