PC shutoff during Migration Assistant transfer to Mac
You will very likely need to delete the user on the Mac side and start the migration again. Depending on your setup, this might be a bad choice of steps, but most people run Migration Assistant as part of the first boot process, so I made the assumption that you also did that. Your next step might be to decide if you want to get help from Apple (they support all new Macs for free through AppleCare and the retail stores) or if you want to provide us with more details and see if we can guide you to how to reset things and start the migration over.