Weird, since I just said it added depth to the character and Hal is literally my favorite Green Lantern.Once characters start doing evil **** and try to justify it they're no longer the same characters, they're no different than the villains they fight. Parallax isn't Hal Jordan, and I'm not referring to the space bug retcon. Hal Jordan isn't the kind of person who will start murdering his friends because he went through a traumatic experience. Hal Jordan isn't Anakin Skywalker, he's not a character who was specifically created with the intention of turning heel, he turned heel because the DC regime at the time wanted to be "edgy", did not see him as important enough of a character and wanted shock value for the sake of boosting sales and bringing in another character to replace him with. On top of it there's nothing original about Parallax as a concept. He is little more than bootleg Sinestro, the former greatest GL who got corrupted by his power and went sideways. Been there, done that.
The people who like Parallax and still insist it "made Hal so much more interesting", "did a lot of good for his character journey" or "makes sense" are mostly those who simply want the character out of the picture so their favorite GLs can get the spotlight and beat him up, while conveniently stealing his content, friends, villains and stories at the same time. When all is said and done, that's really what this has been about. In the past I could give people the benefit of the doubt about this, nowadays it's been increasingly difficult to do so. The notion that making a founding Leaguer a murderer, then killing him off and having him gone for a decade somehow "did a lot of good" for his character is insulting to my intelligence. No it didn't "make sense".