For many who knew the late UN Secretary-General Kofi Annan, he was an extraordinary statesman, diplomat and gentleman. But the tenure of the Ghanaian diplomat who spent more than five decades with the United Nations has not been without controversy. CGTN UN correspondent Liling Tan looks at some of the darkest moments that plagued Kofi Annan's time at the UN, and why despite failures, his legacy endures.

In many ways, Kofi Annan was the United Nations. That is how current Secretary- General Antonio Guterres described his predecessor.

ANTONIO GUTERRES UN SECRETARY-GENERAL "He puts people at the center of the work of the United Nations. And was able to turn compassion into action across the UN system."

A true child of the organization, Kofi Annan began his UN career in 1962, at just 24 years old. Over more than three decades, he rose through the ranks to become secretary-general from 1997 to 2006.

UN spokesperson Stephane Dujarric seen here with his children and Kofi Annan, recalls when he first joined the late UN chief's team in 2005.

STEPHANE DUJARRIC UN SPOKESPERSON "I remember the first time I met him, my boss at that time introduced me to him quickly as he was coming into the building. And I remember feeling overwhelmed by the fact that he was this man that was very powerful. It just took a few minutes to meet his new staff member and junior staff member. And from that moment on I felt very much at home and at ease with him."

It was that humility and approachability that endeared him to people within the UN, and his gentle diplomacy that inspired the world.

NATALIE SAMARASINGHEEXECUTIVE DIRECTOR OF THE UN ASSOCIATION, UK "I think people will remember him for the enormous amount of reform that we saw during his tenure as Secretary-General. The creation of the Human Rights Council, of the Peace building Commission, the adoption of what we now consider flagship initiatives of the UN, the Millennium Development Goals most prominently."

LILING TAN NEW YORK "For his accomplishments, Kofi Annan was awarded the Nobel Peace Prize in 2001. But his time here also saw some of the darkest moments in UN history. His failure to prevent the Iraq War, and to stop the genocides in Rwanda and the former Yugoslavia in the 1990s scarred the organization. Kofi Annan had taken these failures very personally, and tried to atone for them, especially for Rwanda."

LOUIS CHARBONNEAU UN DIRECTOR, HUMAN RIGHTS WATCH "Kofi Annan was not perfect. And in his period before he became Secretary-General in 1997, before that he was the Under-Secretary-General for Peacekeeping. And during that time, the Rwanda situation happened. This was on his watch. The UN did not handle it right. They had information the genocide was unfolding. They had information from the field and they did not ring the alarm bells and run to the Security Council."

Kofi Annan may have been an extraordinary statesman, diplomat, and gentleman, but many say it is his peacemaking spirit and his willingness to acknowledge failures and make up for them, that will endure. Liling Tan, CGTN, New York.