I found this Time Magazine article to be rather interesting:
Death of a TigerThere are many more quotes - from more recent history books - describing Kim's career in this post over at Sperwer's Log, but this Time article is interesting because it's a contemporary source using the word 'terrorist.' More than a year ago, a foreign professor calling Kim a terrorist set off netizen reaction and media attention, though part of his point was that the definition of terrorism has changed since the mid twentieth century. Worth mentioning is that this is the man who will be on the new 100,000 won bill (as soon as they add Dokdo to the map on the back).
Monday, Jul. 04, 1949
Jail, exile, violence and intrigue had been part & parcel of Kim Koo's life for more than half a century. At 19, he killed a Japanese policeman in Korea, served several years in prison. Later Kim Koo went into exile in China, further enhanced his reputation both as an intense Korean nationalist and ruthless political terrorist: To friend & foe alike, he became known as "The Tiger."
Kim Koo was a Rightist, but he soon broke with Rightist President Syngman Rhee. Kim made a bitter fight against establishment of the U.S.-sponsored South Korean Republic, which he felt would permanently divide his homeland.
One day last week, the tired, 73-year-old terrorist was resting alone in a second-floor bedroom of his house in Seoul. Shortly after noon, a young Korean army lieutenant, known to the police who guarded the "Tiger's" home dropped in for a visit. He talked with Kim Koo for about five minutes. Then he drew a .45-caliber automatic and fired six shots; four of them struck Kim Koo, who died almost instantly. Later, police reported that the lieutenant had slain Kim Koo to prevent him from using part of the Korean army "for his own purposes." [Emphasis added]
Personally, I'd choose someone like Sin Chae-ho, seeing how influential his writing and ideas were (as mentioned here). An essay titled "Shin Ch'ae-ho's Nationalism and Anarchism" can be found here.