President Park, not the most original guy, decided to send 31 assassins of his own to kill North Korean leader Kim Il-sung. To that end, the government recruited 31 street toughs and shipped them off to an assassination training camp on an isolated island. The camp's logo was a skull and crossbones made with real human bones, which was not a good sign of what was to come.
Yang Dong-soo/National Intelligence Service
It's important to note that South Korea wasn't rainbows and boy bands under Park, who had come to power in a military coup. Training on the island was so insanely brutal that one recruit died of exhaustion and six others were executed by their trainers. To make matters worse, relations with North Korea thawed and the assassination was repeatedly put on hold, leaving the team completely isolated on Murder Island for over three years. Shockingly, this situation wasn't exactly great for their mental health.
In 1971, the team snapped and murdered 18 of their trainers, which we guess counts as graduating from assassin school. They then escaped to the mainland and hijacked a bus to Seoul. Their exact motives are unclear, but President Park wasn't about to take any chances with 24 rogue assassins bearing down on him, especially not ones he'd personally had trained to kill heads of state and given every reason to hold a grudge. The military killed most of the team in another bloody battle outside Seoul, and the surviving four were later executed. The government covered the whole thing up until the '90s, by which time not even this story could make the South seem like "the crazy Korea."