Introduction:
The Korean president, whose resignation was demanded by citizens through candlelight protests, was Park Geun-hye. This event marked a significant turning point in South Korea's political history.

Background:
- Park Geun-hye is the daughter of former South Korean president Park Chung-hee.
- She became the first female president of South Korea, serving from 2013 to 2017.
- Park's presidency was marred by corruption allegations and abuse of power.

The Candlelight Protests:
- The candlelight protests were a series of peaceful demonstrations that took place in South Korea from late 2016 to early 2017.
- The protests began after it was revealed that Park Geun-hye's close friend, Choi Soon-sil, had exerted undue influence on the president and had been involved in corrupt activities.
- Millions of South Koreans took to the streets, holding candles and demanding Park's resignation.
- The protests were largely driven by a sense of frustration with political corruption and a desire for democratic reforms.

Park Geun-hye's Impeachment:
- As the candlelight protests gained momentum, the South Korean parliament voted to impeach Park Geun-hye on December 9, 2016.
- The Constitutional Court upheld the impeachment decision on March 10, 2017, effectively removing Park from office.
- The court found Park guilty of multiple charges, including abuse of power, bribery, and coercion.

Aftermath:
- Park Geun-hye's impeachment led to a presidential election, and Moon Jae-in was elected as the new president of South Korea in May 2017.
- Park was subsequently arrested and faced trial for her involvement in the corruption scandal.
- In 2018, she was sentenced to 24 years in prison and fined billions of won for her crimes.

Conclusion:
In summary, the Korean president who faced demands for resignation through candlelight protests by citizens was Park Geun-hye. The protests were a response to her involvement in a corruption scandal, and her subsequent impeachment and removal from office marked a significant moment in South Korea's political history.