The Greek hero known for completing twelve labors as a form of penance is Heracles (or Hercules). Tasked with these labors by King Eurystheus, Heracles faced formidable challenges such as slaying the Nemean Lion and capturing the Ceryneian Hind. These labors not only served as punishment for a crime but also as a means of proving his strength and heroism. Heracles embodies the archetype of the hero enduring struggles and seeking redemption through valor.