There was OneCoin, a $4 billion Ponzi whose leader is on FBI’s Most Wanted list:
https://en.wikipedia.org/wiki/OneCoin
(IMHO it’s bizarre that OneCoin never bothered to actually deploy a cryptocurrency. If they had done that and then manipulated its price, they would be just like every other useless cryptocoin and the bag holders would be licking their wounds quietly. The end result would be the same as a plain Ponzi but the FBI would never have been involved because token-utility-innovation-something-something.)