One of this works was to kill the Nemean Lion.
In Nemea, a region of Greece, there was a terrible lion. Twice the size of a normal lion, and with an impenetrable skin. No arrow, no sword, could trespass it.
Hercules went to Nemea, and try to kill the lion. First, he threw arrows; but they bounced against the skin. So Hercules drop the bow and ran to the lion. He fought against him, finally choking him with his own hands.