They don't actually destroy the stone. The ring itself was a horcrux, and Dumbledore destroyed it. The stone that was in the ring was passed on to Harry in the Snitch that Dumbledore gave him.
Wanting to use it to revive his family and apologise for his selfishness in the past, Dumbledore lost his common sense, forget that it was a Horcrux which may have been cursed, and adorned it on his right hand. Almost immediately, the curse triggered, and nearly killed Dumbledore.
Meaning we are all capable of doing superhuman feats of strength, it's just that our brains are preventing this in order to conserve energy. An average human can only activate up to 65% of its muscle tissue, while a trained athlete can go up to 80%.
Android 17 got hugely powerful in Dragon Ball Super due to his training. He was able to up his power level by a lot. Many people say that Android 17 was not SSB level, since SSB grants full ki control, where Goku can hold back, but the problem there, was that Goku was not holding back during that fight.