High voltage is not inherently dangerous. In a dry climate you can easily develop ten thousand volts by lying down in a bed without bedsprings with a long acrylic blanket and pulling the blanket over your head hair with your feet. You can get multiple-centimeter-long branching sparks of static electricity from your finger. The only danger of the activity (to you) is that you might produce enough ozone to irritate your lungs. But the energy of those sparks is limited by your body's capacitance to the blanket.
If you do this in a vacuum you could get X-rays, and if you do it near your cellphone or laptop you can kill them. But it's not dangerous to your body.
However, high voltage with enough power behind it to burn a Lichtenberg figure through your body can kill you pretty darn quick.
electronics die off ESD w/o the xray. I didn't mentioned ESD on purpose as indeed what really matters is energy/joules. If you have a source capable of high power but for too short time it won't be that dangerous either.
Thanks for clarifying, I didn't mean to imply that X-rays were necessary to kill electronics with ESD, just that they could be dangerous to a human, physically, even at low power levels. Killing electronics with ESD indeed does not require vacuum.
