If crypto is banned by all governments (which is almost impossible because some government officials still own crypto on low key), it will affect the economy negatively in the sense that, those who depend on crypto to survive (example; full time traders) will start having financial challenges and also those working for crypto projects will be jobless. If joblessness increases, crime rate might also increase. I doubt if this will ever happen, since I'm very optimistic about the future of crypto (BTC especially) but nobody knows what will happen in future.