Parallax originally was just the name Hal went by when he went crazy with power. However after it was retconned to be a space bug that's an embodiment of fear. So here's the question. Originally Hal was being powered up by the Oa power battery, but with the space bug explanation, what was given Hal all that power? Was Hal exposed to a larger scope of Parallax's powers or was Parallax simply only manipulating Hal and his powers still derived from the power battery? Which would be ironic if it was the latter answer.

The latter, by all accounts, is the answer. In fact, that's basically the only difference between original and later Kyle and Hal parallaxes. The original had absorbed all of Oan energy granting him power over the universe and all. Later parallaxes had no access to such power, making them less of a threat.

it pissed me off that Johns retconned this. Emerald Twilight is the only time i've ever found Hal Jordan interesting. it actually gave him some real character development and the whole idea of a famous superhero going nuts was totally original at the time. 
 
but no... because Johns is such a fanboy of Hal... he retconned it and gave him the ultimate Mary Sue treatment.