Making Hal being mindcontrolled by the so called Fear Entity was DC's greatest mistake.
Not only the retcon ruined Kyle's role as the savior of Green Lanterns.
But it ruined Guy Gardner, he was finally having a role that wasn't "Human Green Lantern number 3", he was Warrior, a vuldarian anti-hero, he was finally his own character, we had an arc of him moving on from being a GL and now it's ruined by him being the cocky jerk he was before.
It ruined John Stewart, years passed at him being in Hal's shadow were finally over, he was finally realizing he didn't need a ring to be an hero, he didn't even need a Darkstar armor, he just needed to be himself. For me he could have been a New Guardian of the Universe if we needed him to be "important" again.
Hal Jordan's character arc ruined, he was finally a serious man, he take seriously his job as Green Lantern and after the retcon he went back to being the young reckless asshole as if he didn't learn anything.
And "parallax was the cause of the yellow weakness of the GLs" is stupid if we consider that we already had the explanation of the Guardians puting limitations on the rings for not making the GLs too powerful.
The retcon ruined the Green Lanterns as whole
I don't even care about the other Lantern corps, I just wanted that status quo to not be god.