You can tell me anything what's bitcoin worst enemy is...
Mine is, government!
I think if there are bitcoin's enemy, it will be the users. We all know that the user's are the most important when it comes to it's value, but even so, the users are the most reason why there are some problems in the blockchain. They keep clogging it, there are a lot of users so there will be always a massive number of transactions. Good thing bitcoin is still being developed.
I agree to the part where you say users only, I may or may not agree with the rest of your statement. I would instead like to have my own statement which is absolutely different from yours. I agree that it's the people who use bitcoins are the enemies or threat to bitcoin but not all of them just a few of them in fact who use it for illegal activities and for crimes and because of that governments think of regulating and legalizing it by bringing laws which can limit or completely ban the use of bitcoin. There may not be any country which may have banned bitcoin but people using it for crimes or any other illegal activity will definitely be the cause of it being banned by government and hence such people are the biggest enemy of bitcoin.