Heracles (or Hercules) is best known as the strongest of all mortals, and even stronger than many gods. He was the deciding factor in the triumphant victory of the Olympians over the giants. He was the last mortal son of Zeus, and the only man born of a mortal woman to become a god upon his death.
Offsetting his strength was a noticeable lack of intelligence or wisdom. Once, when the temperature was very high, he pulled his bow out and threatened to shoot at the sun. This, coupled with strong emotions in one so powerful, frequently got Heracles in trouble. While his friend and cousin Theseus ruled Athens, Heracles had trouble ruling himself. His pride was easily offended. He took up grudges easily and never forgot them. His appetites for food, wine, and women were as massive as his strength. Many of Heracles' great deeds occurred while doing penance for stupid acts done in anger or carelessness.
It would be easy to view Heracles as a muscle-bound buffoon. Indeed, many of the Greek comedy playwrights used his character this way. Even among serious critics, he was often seen as a primitive, brutal, and violent man. There is much evidence to support this view; his weapon of choice was a massive club; his customary garment was a lion skin, with the head still attached; he impiously wounded some of the gods; he threatened a priestess of Apollo at Delphi when an answer to his questions was not forthcoming. He created most of his own problems.
However, viewing Heracles as simply a strong buffoon is unfair. He may have held grudges, but he would also do anything to help a friend. Once his anger passed, he was the most critical judge of his own actions. He was too strong for anyone to force a punishment on him. That he willing did severe penance shows a fundamental sense of justice. During his punishments he showed patience, fortitude and endurance that were as heroic as his strength. Terrible things happened to him because of Hera's hatred, a hatred that he was not responsible for. That he persevered through it all was a moral victory beyond simple strength.
The view of Heracles shifted considerable over time. The early view focused on how badly he managed despite his obvious gifts. As time passed the focus shifted to his virtues. The Romans valued him highly as he best fit their idea of a hero. He eventually had a fair sized cult that worshiped him as a god.
Heracles is also called Hercules.