Some alt-coins have been destroyed by the in-rush of massive hashing power, which caused a difficulty-adjustment up, followed by an exit of that hashing power,

Some alt-coins have been destroyed by the in-rush of massive hashing power, which caused a difficulty-adjustment up, followed by an exit of that hashing power, leaving block-progress so slow that it would take 'forever' (impractically long) for the next normal compensating adjustment-down to happen. Since one of the joys of Bitcoin is using it to exercise one's paranoid imagination, consider scenarios where somehow, an enemy of Bitcoin (or promoter of an alternative) can somehow disable or redirect all that ASIC power in a short time frame. Perhaps, in cahoots with the ASIC makers, some magic input can cause them to begin malfunctioning (either temporarily or permanently). Or, a cartel controls enough SHA256 power to withhold capacity, and switch to a NewCoin needing the same hashing resources, in rapid coordinated succession. Or both. It might be hard for Bitcoin-prime to adapt in time, while NewCoin's deep-pocketed backers from the USG, CCP, or evil lectroids of Planet-X tempt miners and Bitcoin balance holders to switch to NewCoin, perhaps via an initial endowment mechanism which requires the irreversible destruction/relinquishment of old Bitcoin balances. Ah, good times. Good Stephensonian-science-fictional times.