Final answer:
Herakles' first demonstration of his superhuman strength and heroic abilities was slaying the Nemean Lion, which was his first labor of the twelve he was commanded to complete as penance. The lion's skin became his iconic garb, featured in many pieces of classical art.
Step-by-step explanation:
Herakles, also known as Hercules in Roman mythology, demonstrated his superhuman strength and heroic abilities for the first time by killing and skinning the Nemean Lion, which was the first of his Twelve Labors. These labors were tasks he undertook to atone for his madness-induced murder of his family. The Nemean Lion was a fearsome beast whose hide was impervious to weapons, making this feat particularly notable as Herakles accomplished it with his bare hands, representing his incredible might and bravery.
The labor involving the Nemean Lion is not only significant because it was the first task but also because Herakles wore the lion's skin as a cloak thereafter, which became a distinctive attribute of his depiction in classical art. For example, on a storage jar from fifth-century B.C.E. Greece, Herakles is identified by his black hair, beard, and the lion-skin cloak that signifies his identity and illustrious feat. Statues, such as the one by Lysippos, further glorified his strength, showing Herakles in a muscular form leaning on his club after his victory over the lion.