QuadrigaCX

What happened

Canada's largest exchange at the time told customers it could no longer access roughly CA$190M in funds after its founder died while allegedly holding sole control of the cold-wallet keys. A later court-appointed investigation found many of the wallets had been empty long before his death, pointing to mismanagement and likely fraud rather than a pure accident.

What to take from it

Single-person key control is a structural failure waiting to happen — deliberate or not. A credible custodian never lets access depend on one individual.

Dates and figures are widely reported public estimates from coverage at the time, not KripZen's own audited data.