Hal Jordan's time as the villain Parallax may have convinced a sizeable portion of fans that Green Lantern has a dark side, but his lesser-known possession shows that the hero is actually pretty harmless.
When Cyborg Superman ordered the destruction of Coast City, Jordan went insane with grief and, shortly after, became the multiversal threat known as Parallax. DC caused a huge controversy by turning Green Lantern evil, both in universe and out. While his comrades were shocked for years at the Lantern's turn to evil, it was later revealed that Hal's descent was actually the result of being possessed by an ancient entity also known as Parallax. After this revelation came to light, many in the hero community welcomed Green Lantern back into the fold, save for a few doubters such as Batman. Despite Hal being let off the hook, some felt that Parallax simply exploited feelings that Green Lantern had deep within. But the Emerald Knight had a brief experience with another malignant entity that may prove Hal's innocence once and for all.
In Green Lantern #42 by Geoff Johns, Philip Tan, and Eddy Barrows, Jordan faces off against Larfleeze, aka Agent Orange, the sole possessor of the Orange Lantern Power Battery. In the same way that the Green Lanterns are powered by will, Larfleeze is fueled by insatiable greed. As the two fight one another, Jordan recognizes that the battery Larfleeze refuses to let go of is helping keep his ring fully charged, allowing him to pump out hundreds of constructs. Taking advantage of a brief distraction caused by the Guardians of the Universe, Hal latches onto the battery and seizes it from Larfleeze's hands. Green Lantern is overwhelmed by thoughts from a mysterious voice, who urge him to indulge in his desires which include, strangely enough, a couple of burgers.
The voice that comes from within the Orange Lantern battery actually belongs to a being known as Ophidian the Tempter. Much like Parallax or Ion, who serve as the entities for the Sinestro and Green Lantern Corps, Ophidian powers the Orange Light and is capable of making people succumb to avarice. But interestingly enough, Hal's intense desire for junk food may serve as a great example of why he's genuinely not responsible for his actions as Parallax.
When Jordan lost his home, he was emotionally weakened and felt more fear than he ever had in his life. As the entity of fear, Parallax was able to use that as an opening to possess Hal and use his powers for Parallax's own malicious agenda. People targeted by the incredibly powerful entities of the Emotional Spectrum may harbor certain feelings, but once they become a host, their actions are no longer their own. Similar to Parallax, Ophidian recognized that Jordan had a minor capability for greed, but it was the exposure to the entity that changed Hal into a monster hellbent on owning anything and everything. Fans eager to condemn Hal Jordan should take a look at how the Emotional Spectrum's entities operate before making a final judgment.