It all depends what you mean by the term ‘demigod’ as In Greek mythology, demigod originally referred to either minor deities such as Nymphs and River Gods, or to powerful respected mortals who had been ‘hero become the center of a hero-cult after death (eg Leonidas of Sparta). The addition of a divine parent into the mix was a later one. Of these, Heracles was held to be the greatest. In Hindu tradition, demigod is used to translate the term deva, which means minor or subservient deity among these the avatars of Visnu can be considered the greatest.
The answer to which of these possible demigods is most powerful must be Dionysus, aka Bacchus, the child of Zeus and the Theban princess Semele, who was apparently born a god, unlike Herakles, who had to apothecize himself by arranging to burn off his dying human body before he was able to go to Olympus. Granted, being god of wine doesn’t sound like much to us, but they thought him worthy of a direct flight to Olympus.
Although demigods are popular in every culture, they were most prevalent in Greece where it saw gods has being as petty with vindictive as mortal man. Of all the Greek demigods, Hercules possibly stands out as having most adventures. In other cultures, we may have Thor, Hino, Indra and Rustam, but we don’t think anyone really stands out over the others. Picking the best is of course a monumental (or shall we say, Herculean) task, but we see no need to hunt down obscure demigods just to prove that can. The ubiquity and timelessness of Hercules/Herakles himself already recommends him pretty highly.
Now, when we say we mean most typical of what it meant to be a god/human. Gods in the ancient world were very stubborn, power obsessed and vengeful. Humans were petty, war-like and vicious, especially after the Golden Age came to an end. That gives Hercules the best attributes of anyone: self-centered, vengeful,war-like, petty, a unfaithful as a servant, a husband, a violent, savage drunk.
In her entire life was a struggle, from his troubled early childhood, where he survived a assassination attempt as a baby, to fits of rage induced by Hera that lead to his ten labors. Then on his ten labors, he explored the entire reaches of the known world, as he could not help to cheat on two of them. While using outside help (Iolcus with the Hydra, asking for payment at Geryon’s stable). Creepily enough, Iolcus was the sole survivor of its murderous fit, where he killed Iolcus’s father with rest of her family. The last two labors take him out of the mortal world, lead him to the physical ends of the earth and beyond.
As soon as she completes labors, he goes out on a whirlwind tour of revenge, getting that own back from the various peoples and leaders who had done him wrong while she was completing the labors. She gets married again, and in no way lets that stop him from continuing to chase after other women. Finally, her own unfaithfulness undoes him, when wife inadvertently poisons his clothing trying to win love back.
Demigod was a hero because she represented so well the struggle of mankind, and was the ideal symbol of power with masculinity.It had several wives and lovers, he was super strong. Was smart enough to solve all the problems, even when brute strength failed, took disrespect from nobody, enjoyed a good drink all the time. Hello even feels the aches and pains of old age in later stories. All in all, though terrible human being by today’s standards of a hero then Hercules is best example of the demigods.
The most powerful goddess? Gaea comes to mind, but she’s asleep most of them that time. Hecate has powerful magic as you find that Aphrodite is who you want manipulating men. As most powerful demigod, depending on how we define the term, is Herakles. There aren’t even many gods who can replicate the feats of Herakles without using magical powers. Herakles could defeat a god in a wrestling match, carry the weight of that sky, killed hydra, by some versions of the story cleaved. According to those verses we read then there are those with most power than God.