Get all the governments in the world to "Ban" Crypto currencies..... but just remember one thing, before you start.... There is almost nothing that the world governments will ban... if they can benefit from it. Take Russia for instance.... they are currently using Crypto currencies to bypass the global sanctions... so good luck getting them to change their mind now.  

Also... a ban of Crypto currencies will push it underground and then it will be almost impossible to stop. (The government will also then loose millions in taxes, because these underground transactions will not be taxed)