IMO, the worst case scenario is that the price of Bitcoin doesn't rise faster than fiat inflation for 5+ years, which would make mining for most unprofitable. The less efficient miners would sell their hardware for cheap, would provide an opportunity for nation-states to buy enough hardware to begin 51% attacks.

The world is going into an economic depression, during which a lot of people will sell a lot of cryptocurrency in order to pay for basic necessities. Bitcoin will be hit by that wave of sell-offs. It will be a great time to buy more BTC, if you are frugal enough or have a fiat job that can keep you afloat for a while. But for everyone else, they will be expending their savings just to survive. If the price of Bitcoin does not rise fast enough, then a lot of people will run out of Bitcoin before the depression is over.

All that being said, I am betting that Bitcoin will rise faster than fiat inflation, because all other bets (gold, holding cash, investments, etc) are guaranteed to be losing bets during the upcoming depression. Bitcoin is the only thing that has any possibility of being a winning bet.

If Bitcoin fails, so does the global economy; there is nothing else that can save the international devision of labor. The fiat monetary regime has squandered a lot of the global supply of resources on useless projects. Only Bitcoin has any change of rebuilding after a century of escalating waste.