I really don't know if there is an actual way to kill off Bitcoin, unless it simply becomes irrelevant and people stop paying it any attention. That's the only way that I can really think of to stop Bitcoin, is for it to become irrelevant. Also if the governments around the world really wanted to play ball, they could simply prohibit the exchange of cryptocurrency into fiat and pass a law for the banks ro stop dealing with customers who make cryptocurrency related transactions.
   This could really deflate the market something serious if people were forced to hold their bags and not be able to exchange their crypro into fiat.