held the Guinness World Record for highest IQ at 210 . He could
absorb languages like a sponge-- not just rote memorization but also
thoroughly grasping grammar and nuance. At age 3, he was attending
physics lectures at Hanyang University. He could read Korean, Japanese,
German, and English by the time he was 4. When he was 8 he was invited
to the U.S. by NASA, where he earned his masters and PhD at Colorado
State. Afterwards, he worked as a nuclear physicist and researcher at
NASA for 5 years until the ripe age of 16, upon when he suddenly wrapped
up his life overseas and returned to Korea.
curiosity (and dismay) he enrolled in a 'no-name' university and studied
civil engineering. He originally couldn't even apply for university
because he'd never graduated from high school, and had to get his GED.
He was an ordinary office worker for a while and gradually faded from
the memories of the Korean populace.
His own thoughts are as follows... (from an interview)
but I am not a genius. I just happened to learn things a little faster
than others. Learning things more quickly doesn't mean that you go
further in life. 
"After I returned from the states, I chose
my school and my workplace as I pleased. What I'd studied in the past
was for destructive purposes, but my new major (civil engineering) was
to create useful objects that had never existed before, and I enjoyed
that. My current workplace is the same way. However, the things that
brought me happiness incited a different reaction from the rest of the
world. No matter how often I said "Right now, I am happy," others told
me, "There's no way that's possible." If I say, "I am satisfied in my
work," they respond with, "Why would you even..." I was called a genius
in the past, and it seems that that means I must be a professor at
Harvard or Yale. I will say this again: I am happiest right now." 
The interviewer still didn't get it. "But why did you throw it all away?"
"To become happy. Even when I was in the U.S. I heard that I was fairly talented. But I didn't know what I was talented at.
All I did was solve problems and equations like a machine. For one
division, there were more than twenty different research labs, but you'd
never even know what was going on in the room next to yours. Secrecy
was most vital, and any important milestones were attributed to those in
superior positions. Perhaps the most problematic thing was that there
was no one to listen to the small voice of a young boy. I could see no
escape. I wonder, now, if there were similarities between the recent
suicide of the KAIST students and my situation back then." 
I don't believe Kim threw anything away. He let go of something that he
didn't want and didn't need in order to grasp hold of something better.
The simple joys of a normal life. He could have become almost anything
he wanted to be, and he chose happiness.
Today, Kim Ung-yong is
52 years old, and recently fulfilled his dream of becoming a full-time
professor. He lives a quiet life, staying out of the eyes of the media
and investing in the young minds of his students.
"When I am
kicking around a ball with my son, or getting a drink with my colleagues
after work... That is when I am the happiest."
NB that 2-5 are the original texts, which have been translated into English in the main answer.
The Guinness Book of World Records retired "Highest IQ" in 1990 because
they thought it was an unreliable test. Otherwise, Kim might still be
holding that record.
 "죄송하지만 나는 천재가 아니다. 남들이 살면서 천천히 배우는 것을 조금 어린 나이에 익힌 것일 뿐이다. 빨리 익혔다고 멀리 가는 것은 아니지 않나."
"미국에서 돌아온 뒤 학교든 직장이든 내가 좋아하는 곳을 선택했다. 그 전에 공부하던 분야가 파괴를 위한 것이었다면 새로 배운
전공(토목공학)은 없는 것을 만들어 사람들이 이용하도록 하는 일이어서 좋았다. 지금 다니는 직장도 마찬가지다. 그런데 내가
그렇게 좋다는데 세상의 반응은 내 생각과 달랐다. 아무리 내가 “지금이 행복하고 좋다.”고 해도 사람들은 “그럴 리가 없다.”고
했다. “내 일에 만족하고 있다.”고 하면 “왜 그런 일을….” 뭐 이런 식이다. 과거에 천재라고 불렸다면 지금 내가 반드시
하버드대나 예일대에서 교수를 하고 있어야 하는 것인가. 다시 말하지만 난 지금이 가장 행복하다."
행복해지기 위해서다. 난 미국에 가서도 꽤 잘한다는 소리는 들었다. 하지만 내가 뭘 잘하고 있는지 몰랐다. 주어지는 과제와
수학문제를 기계처럼 풀기만 했던 것이다. 한 분야를 위해 20개 이상 연구실이 함께 작업을 했지만 정작 옆방에서 뭘 하는지는 알
수가 없었다. 비밀주의 원칙이 이어졌고 거기서 생긴 공은 대부분 윗선의 차지였다. 어린 나이에 힘들다는 내 하소연을 들어줄
사람이 없었다는 것이야말로 가장 큰 문제였는지도 모른다. 어디에도 탈출구는 보이지 않았다. 최근 자살한 카이스트 학생들도 나처럼
그랬던 게 아닐까 싶기도 하다."