10. Seo Jung-Jin

Loss: $1.6 billion

Seo Jung-jin is the founder and chairman of Celltrion, a South Korean biopharmaceuticals group that develops drugs to treat cancer, influenza, rheumatoid arthritis, and other maladies.

Celltrion's stock price slumped by about 15% in 2019, slashing Seo's net worth to $5.1 billion.

One reason for the stock drop was JPMorgan-owned One Equity Partners' sale of a 4.5% stake in Celltrion for $327 million in May. The move followed a billion-dollar stock sale by another key investor — Singapore's sovereign wealth fund, Temasek — in October 2018.