the first Quantum Computers will be very few and owned only by large governmental or private organizations, until technology advances to the point it could reach the masses
They would build a quantum computer intentionally for Bitcoins case to frack the 'Shalecoins'. ('Shalecoins', coins with no owner '
https://bitcointalk.org/index.php?topic=5134441.0)
Banks can freeze accounts, rewind, correct it.
But Bitcoin can't.