Mt. Gox (Mount Gox) is one of the most notorious exchange scams in crypto history.
Launched in early 2010 by Jed Mcaleb, and later bought by Mark Karpeles Mt. Gox was a Bitcoin exchange based out of Japan that dominated handled 70% of all Bitcoin trading volume up until 2014. Filing for bankruptcy February 28, 2014 after a series of suspicious hacks and thefts Mt. Gox halted all withdrawals and claimed that approximately 850,000 Bitcoins (worth ~$450 million at the time) dissapeared.
After years of litigation and international man-hunting, Mr. Karpeles was found guilty of financial fraud and the people whom were robbed have begun to receive reimbursements. As of Summer 2020, 200,000 Bitcoins have been returned to the rightful owners.