They could never 'Kill' the Bitcoin, some big governments like China have tried but seems like failed to do so, they can restrict the use, restrict the access but an individual will always find a way to access his account. I am not sure if a government can even impart Tax on crypto industry as there are always to perform anonymous transactions. So the answer is NO.
one thing they can do is to buy all Bitcoins, but the last few to sell bitcoins may hav millions of dollars for a fraction of bitcoin, even more beneficial for the ones hodling bitcoins.