A government ban is one of such scenarios. If the government makes the possession of Bitcoins a criminal offense, then very few people will be willing to take the risk.
I think that is not the thing that can bitcoin die because now there are some country which bitcoin is already ban but lots of people there are continuous collection bitcoin using vpn.
Yes, it does not destroy bitcoin. Many users already simply can not do without it and they will have to go through the trick.