Methods that might work, or only impact some functions of your Duet
Reverse the VIN power connections. Preferably, use an old-fashioned unregulated power supply - basically just a transformer,
bridge rectifier and smoothing capacitor - without any form of current limiting. That should guarantee that you at least fry
all the stepper drivers. Don't be tempted to do this using a modern switching power supply, because these generally have
foldback current limiting - the lower the output voltage, the more the current is limited - so the current may be too low
to fry the drivers. Remember, there are 5 drivers connected across the VIN supply, which will share the current.
You need to supply enough current to fry all of them together. Even if you do fry the stepper drivers, you probably
won't fry much else, because the 5V regulator is protected by a diode. Stepper driver chips can be replaced,
so although frying them all is a good start, it's not a way to completely write-off your Duet.