The government and the Central Banks are the worst enemies of bitcoins . Even though , many countries has legalised bitcoins but still no country wants to accept it as a primary form of currency because no country wants the loss of their currency and funds.
Bitcoins gives threat to Central Banks because bitcoins are purely decentralized and backs has no control over them .The popularity and legality of bitcoins will lead to a huge loss for the Central Banks and they will never let that happen. Bitcoin is a threat to the cliche form of finances.

Aside from governments. It's banks. They do not want to decentralize anything.

Banks and government are the most likely opponents of Bitcoin due to them having control over the currency and Bitcoin interferring. But in more reasonable situations government can be pro-Bitcoin.

The people who want to Control Bitcoin, As we all see how powerful bitcoin at present, banks and financial business already considering its technology to be adapt on their businesses, No one owns bitcoin that's the nature of it a decentralized, however if someone or somebody successfully controls this then its not the real Bitcoin that I knew its his enemy.

other than that electricity and internet i think is also influential. because electricity and internet needed to mine and do transaction, if government policy I think not too influential. because now in my country bitcoiN is still in unambiguous status legality, but the government does not forbid it. therefore bitcoiN is still developing in my country.

I think banks can be ennemies for bitcoin and altcoins. Banks will loose many clients who moves to put their money in bitcoin instead of banks.

Mine is users too! Well bitcoin serves us dear users with its servicea, but I think that we users can also formulate the end or be the worst enemy of it.
First is the non-patronage well seems like it is impossible but to tell you the truth, it is possible. If people would turn their backs on bitcoin, then there is a possibility that it will become worthless.
Second, with the high end technology comes the high end attacks of it. Users or anti bitcoin can formulate a way for some malware to come into the system. Making online wallets vulnerable to hacking and unauthorized transfers.
Lastly, are the banks. They can move for a resolution to ban pemanently bitcoin because of the threat that the government will not profit from it like banks do.
These are just my opinion.

The bankers teaming up with the government. Once they combine forces then digital currency suffers. They know that users of cryptocurrency are still vulnerable because it is new so a rumor or news spreading FUD would have a big effect in the price and we have seen it recently. Bankers and the government in China decided to ban crypto trading in their country because financial institutions are threaten by it so as a protection for them, government bring up licensing so that they would still have control. Bankers losing their business and government losing their control would be the worst enemy of bitcoin.

Bitcoins biggest enemy is not any government or other force. It simply isn't. Governments cannot realistically stop it at this point. Unless they shut down the internet.

The only threat is a new, better cryptocurrency. Bitcoin is not perfect by design. For its time, it was incredible. Now, however there are new technologies that make for better cryptos. Bitcoin is left behind in that regard. And once a coin comes along that is significantly better in most or all respects, I think Bitcoin will actually die off quite quickly.