The god Helena makes Hercules kill his own family by making him go insane
As punishment Hercules serves the king for 12 years and must complete 12 impossible labors.
Hercules's First labor was to kill the Nemean lion. Its hide is so thick that it cant be pierced by sword or spear so Hercules strangles it to death.
you have done well, my son
Hercules's second labor was to kill the lernean hydra that was terrorizing the neighboring villages. The only problem with this is when Hercules cuts one head off two more grow in its place. When Hercules cuts one head off he cauterize the wound so the head would not grow back.
For his last labor Hercules had to capture the hellhound Cerberus and bring it back to the king for proof. Hercules does this by wrestling the hellhound into submission.
After Hercules completes his 12 labors the gods of Olympus made Hercules immortal.