One of the most morally ambiguous things which can happen to a character is the possession of that character (meaning here that the actions of that character are beyond their control.) Possession throughout the majority of literature has generally focused around some sort of diabolical power but with the advent of science fiction it has become possible that new forms of possession have resulted without absolute evil necessarily being associated with it. In terms of how the heroes are portrayed there is some level of a discrepancy when it comes to their actions. Take for example two cases, Hal Jordan being possessed by Parallax and Superman being possessed by Maxwell Lord. In both cases the heroes are acting against how they regularly would, but there are generally a few who would argue that Hal's actions make him a criminal whereas Superman's do not affect his hero status. In terms of the actual actions of the heroes while possessed it is not terribly different in terms of intent if only time restricted the scale of Superman's actions. Hal Jordan wanted revenge for the destruction of Coast City whereas Superman was being used to destroy the world's superheroes starting with Wonder Woman. Although Superman never actually killed anyone it was still a possibility after having thrown Diana from outer space onto a highway. Hal on the other hand did kill some people, other Lantern members as well as Sinestro and many of the Guardians. Actions are important here, but if intent is an indicator then there is not difference between the two, thus if someone says Hal Jordan is a villain then Superman must equally be one. The difference in the scenario perhaps comes from the conditions of the portrayal of the characters. Superman is generally viewed as the paragon of a stable character, in that he is mostly incorruptible. The depiction of Hal though is that he partially aided his possession by wanting revenge against Hank Henshaw and Mongul. Revenge is generally not a particularly bad feeling, rather is depends on what you do with it. For instance, Batman has based a large part of what he does on revenge or at least a retribution or reckoning but again here there is a disconnect. in one case the desire for revenge forces Bruce to become a great hero, in the other it caused the person to become possessed while emotional fragile and become a villain. I would say overall that the interpretation that Hal is a villain is inaccurate. It was not heroic, but he was not in control of his actions and he only reached that point by being human. The fact that he eventually overcame it is the true mark of hero.