Quadriga was Canada's largest crypto exchanges, and has the most colorful story of any exchange. They weren't hacked, but they still managed to lose $190 million dollars worth of customer's cryptocurrencies.

Quadriga did one thing right. They had the majority of their customers' assets in cold wallets. The problem, however, was that the wallets were only accessible by the founder and CEO, Gerald Cotten. While on his honeymoon in India, Cotten suddenly died, taking the passcodes with him to his grave. Leaving the cold wallets completely inaccessible.

Furthermore, the business had a variety of other fishy things:

• As investigators dug into it, five out of six of the cold wallets had been emptied out two months prior to Cotten's death.
• Quadriga had no bank accounts, and only used external payment processors, all of which have been named in civil lawsuites for hundreds of millions of dollars. 
• Cotten's will was also signed twelve days before he died.
• They had an usual withdrawal system where customers were told to go to an address in Laval, Quebec to pick up their cash. Customers report to finding no one there, and no cash to withdraw.
• Previously they had claimed to have lost $14 million worth of Ethereum due to a smart contract error.

Because of these strange circumstance, some redditors have claimed that Cotten faked his death to escape prosecution.