I can think of a lot of things but the infamous Mt. Gox hack was, for me, the biggest crime made in the cryptoworld. Not only does it expose a lot of flaws and vulnerabilities of the then young cryptocurrency but it also projected the dangers of having to entrust one's funds into a centralized exchange/entity. The next in line would have to be Silk Road, which was operated supposedly by Ross Ulbricht, which, again, informed the world about the possible use of bitcoin in the criminal underworld due to its pseudo-anonymity, hard to trace transactions and its overall qualities which is pretty much helpful in remaining anonymous while transacting with other people.