What could kill Crypto?
Cryptocurrency will stay in my opinion in one shape of another. Call it bitcoin, ethereum or "fed coin" or any other form it will survive. As long as there are 2 nodes running then you have the coin that is working. Governments banning bitcoin exchanges and closing up the fiat gateways could kill mass adoption but overall can't stop it and so far this is the biggest bad thing that could happen in my opinion. Of course you have to have good light wallets and other tools developed so that average Joe can safety use bitcoin or any other cyrptocurrency without knowing he is using it.