Board Thread:General Discussion/@comment-23932365-20150118201551/@comment-3146930-20150208143024

Even if Poseidon can cause earthquakes, not every demigod receives every power their godly parent represents. For example only Leo has power over fire while Piper has charmspeak. Even the children of Apollo don't have prophecy, but instead have talents in music, archery, and/or first-aid. It is more like a super-power lottery unless a god decides to give you a power.

As far as Percy fighting gods, during his fight with Ares he managed to injure the god, but Ares for the most part was toying with him. After Percy stabbed him, Kronos intervened and Ares retreated as a result. If the fight had gone on longer, Percy most likely would have been destroyed. Phobos is a minor god, so the difference in power isn't that much (powerful demigod is almost as strong as a weak god).

With Hades it is a little different. Yes Percy managed to pin him to the ground, but we find out later from Apollo that because Percy has the Curse of Achillies, he is in the hands of the Fates. Hades once he was pinned down by Percy may have known the same thing and backed off instead of continuing the fight. His original plan was to capture Percy, but if the two had a full on fight, then Hades would risk killing him and even Hades won't mess with the Fates.