South Korea's stock market crash turned into a region-wide sell-off, bad news for retail investors across Asia who got wiped out.

• Many Koreans held funds that multiply gains and losses by three, so a 10% drop in a stock like SK Hynix meant a 30% loss.
• These funds have to sell as prices fall to keep their leverage, so each sale forced more selling and sped up the crash.
• The panic spread beyond Korea, erasing more than $600 billion from Asian markets, with Japan, Taiwan, Hong Kong, and China all falling.
• Korea's market only stopped dropping because it closed for a national holiday, and the president called an emergency meeting to calm things down.

Outlook: The dangerous leverage is still in the market, so more sharp drops could follow.