A strong push against Bitcoin by top world powers such as the US. This would heavily impact the price and I think it's the most likely thing to happen.

Things such as Quantum Computers are repairable. I'd have to guess if QCs turned out to be a real danger, we'd just fork off Bitcoin to a QC-resistant fork. There are ways to go around it, even if the impact's already been done. Solar flares really do create way larger issues than Bitcoin though, although the article says this shouldn't be the right way to think. Like, I'm sorry but I think the world would immediately go absolutely crazy if all communication was suddenly cut by such an event. It's similar to EMP attack scenarios - I would care more about my safety and life than about all those devices that'll be affected by it.