This is the year that brought a $100 billion venture capitalist to his knees.

In January, SoftBank Group Corp.'s Masayoshi Son was riding high, writing billion dollar checks to unicorns from office-sharing startup WeWork to autonomous delivery vehicle designer Nuro. But as 2019 winds down, the deal-maker is straining to finance a $9.5 billion bailout package for Adam Neumann's troubled startup, whose valuation has evaporated from $47 billion to $8 billion — or even zero, depending on whom you ask.

SoftBank's bad year goes well beyond WeWork. Investors are starting to get the feeling that whatever Son brings to the public is troubled. And you don't need to look far for proof: Shares of Uber Technologies Inc. and Slack Technologies Inc., both backed by the Vision Fund, tumbled upon listing. To venture funds that rely on IPOs for exits and profit, this dark suspicion is a kiss of death.