I'm not exactly sure your question. Thermal failure of an IC can happen from overheating, which can result in either melting the package, or thermal expansion causing a separation between gate oxide and conductor.
Additionally, heat increases electron tunneling and slows semiconductor switching, resulting in lower stability and/or a lower tolerance for high clock speeds.
Finally, thermal stress can cause damage to components over the long term by repeatedly cycling the heat within the IC. This is a pretty minor thing, but constantly powering up and powering down a device can cause minor reductions in lifespan due to this.
However, 60-70c is no big deal in a modern GPU, as they are often rated much higher (maybe 90c).
Sudden power loss can lead to spikes in voltage in transformers, where the collapsing magnetic field feeds back into the coils and can make a several thousand volt spike. Decent electronics are well protected against this, but if protections have already failed, it certainly is possible to cause damage this way. In a modern computer, this is exceedingly unlikely.
In a very old all-analog television, I think this explains why the volume often spikes loudly at the moment the TV is switched off, as the excess voltage hits a number of areas in the circuitry.