One of the biggest bitcoin hack to date happened in 2016 from the cryptocurrency exchange Bitfinex.
According to blockchain analytics firm Elliptic: "94,643.29 bitcoins ($3.55 billion) have been moved in 23 transactions, from a wallet associated with a theft from Bitfinex in 2016, to a new address"
The number of bitcoin transferred amounted to 79% of the total 119,756 bitcoins drained from Bitfinex in 2016, one of the biggest bitcoin hacks to date. So much bitcoin! imagine the value of bitcoin from 2016 when they hacked it compared to it's value now! hackers just held into the coins and just started to move it.
Also according to an article from coindesk:
Whale Alert had earlier reported on this development, saying that bad actors transferred 10,000 bitcoins worth more than $383 million to an unknown wallet during Asian hours on Tuesday.