Satoshi is one of the biggest risks: if he shows up and turns out to be a pedophile, sells all of his coins, makes weird statements, etc there could potentially be such a big exodus that the project could fail

Big bug in the code: very unlikely at this point, but there's a possibility that a bug exists and that someone could exploit it. Same as above, if Bitcoin has a bug, everybody is going to freak out and leave

Governments heavily restricting the internet, freedom, and human rights: this one is a little bit more tricky, but in a very very censored environment only a tiny fraction of the population ("the resistance")would still use Bitcoin. Also, if the sheeps in such scenario are "intellectually" unable to choose to use Bitcoin, that's also a failure (I guess a much broader failure though)