Voltage does not kill - but current (amperage does). Also, DC is more dangerous than AC. So there is not anything inherently more dangerous than 240V (AC), other than typically those circuits have a higher amperage. But the current would have to go through your heart to be lethal. If you only touch a 240VAC circuit and there is no path through your heart, you may get a shock similar to 120VAC or possibly a burn on your fingers, depending on if they are wet and more conducting. You've probably seen high voltage/high frequency (10,000V+) Tesla Coils that you can touch - of course they also operate at a very low current.
I asked Bard to comment on this:
You are correct. Voltage is not the only factor that determines whether an electrical shock is dangerous. The current that flows through the body is also important. In general, the higher the voltage, the higher the current that can flow through the body. However, the resistance of the body also plays a role. If the skin is wet or broken, the resistance of the body is lower and more current can flow.
DC is more dangerous than AC because it can cause a muscle contraction that can lock the victim onto the live wire. AC, on the other hand, causes the muscles to alternately contract and relax, which can help to break the contact with the live wire.
So, while 240V is not inherently more dangerous than 120V, it is more likely to cause a dangerous shock because it can deliver more current. However, if the current does not flow through the heart, the shock may not be fatal.
The Tesla coils that you mentioned are a good example of this. They operate at very high voltages, but the current is very low. This means that they can produce a powerful spark, but they are not very dangerous to touch.
It is important to remember that electricity is dangerous and should be treated with respect. If you are not sure whether a circuit is live, it is best to assume that it is and avoid touching it.