There is nothing yo0u can do with MSI Afterburner or similar tools which can break anything, without:
a) Physically modifying the card
b) Putting in a hacked BIOS
c) Starving it of air flow.
While competitive overclockers use a set fixed voltage on the CPus in the hopes of moving up a notch or 2 on website leader boards, practical overclockers who use their machines 24/7 normally won't do this. Instead they will use an offset or adaptive method in whioch in idle, your CPU is sitting at 800 Hz and only climbes to the OC level when the load placed on the CPU can use it.
GPU overclocking, normally, works the same way. Yes, you can lick the voltage on a GPU, but it has no practical value. When you slide the voltage bar up to max and the power up to max, it will on;y 'go there" when you have the GPU under max load. nVidia has loicked their cards down so hard, both legally and physically as to what can be done overclocking wise, that you would really have to make a very special effort to damage today's cards.