This is "Walkin' Backwards," a new feature where I look into how superheroes who turned to villainy were walked back from their heel turn and turned into superheroes once more.
I figure we might as well start with the most famous example of this sort of thing, which was Hal Jordan going full out villain in the mid-1990s. This heel turn lasted pretty long, roughly a DECADE before it was overturned!
It all started, oddly enough, not even in Green Lantern's actual comic book series. You see, back when Hal Jordan first started out as Green Lantern, he operated out of Coast City, a sort of DC Comics stand-in for Los Angeles, the way that both Gotham City and Metropolis were stand-ins for different aspects of New York City (Metropolis, the whole "wow, this is a big city" aspect of it and Gotham as the whole "wow, this is a dangerous big city" aspect of it). Then Hal moved on from Coast City and by the early 1990s, Coast City was only very rarely used. It wasn't COMPLETELY ignored, but it definitely did not show up all that often. So, when the "Reign of the Supermen" storyline started in the four Superman titles, where four different versions of Superman showed up after the Man of Steel died, Coast City was used as the target of an attack by War World that was orchestrated by one of the four Superman - the Cyborg Superman, who turned out to be a short-lived villain of Superman's from, like, three years earlier called Hank Henshaw, who teamed up with Mongul of Warworld to mess the Earth up. So, they destroy Coast City.
Hal showed up, of course, and he was not happy (also of course), but he handled it pretty well at first. Just basically, "This is for my friends!" as he fought back...
He teamed up with Superman and they took down Cyborg Superman and Mongul.
However, when he started thinking about it more, he felt more disgusted by what happened. All of these innocent people killed for no reason and everyone was just, like, "We have to move on." Hal wasn't ready to do that, so he tried to use his ring to, in effect, recreate Coast City.
He even imagined their conversations with him, including his dead father telling him how disappointed he was in Hal.
Hal's ring runs out of its charge and the Guardians are, like, "This is not okay!" but Hal instead decides that his problem is that he does not have enough power, so he decides to take over the power of the entire Green Lantern Corps!
The Guardians send Green Lanterns to stop him and he defeats them all and even takes their rings, making him more and more powerful.
His frienda try to stop him, but by this point, Hal has come up with the position that what he's doing makes it okay if he hurts or kills people, because once he's acquired enough power, he'll fix everything.
He kills his old buddy, Kilowog, and takes control of the Central Power Battery....
He then fights all of DC's heroes as Parallax, with the intent of rebooting the DC Universe, only better....
They stop him and he becomes a recurring Green Lantern villain over the next couple of years... before the FIRST attempt to redeem him!