#6. The Sinestro Corps War
Throughout the years, the tarnished former Green Lantern, Sinestro, has always served as a uniquely qualified nemesis for Hal Jordan and the other Green Lanterns thanks to his yellow power ring, which the Green Lantern's green rings were powerless against. After both he and Jordan returned to active duty in “Green Lantern: Rebirth,” Sinestro re-grouped and returned in “Sinestro Corps Special” #1, this time in charge of a whole corps of allies specifically recruited for their ability to instill great fear. The ensuing Sinestro Corps War was written mostly by Geoff Johns and Dave Gibbons, with art by Ethan Van Sciver, Ivan Reis and many others.
Their first task was to launch an assault on Oa and free two of their prisoners, Superboy Prime and the Cyborg Superman, and in the attack, they also captured Green Lantern Kyle Rayner, who was at the time host to the powerful Ion entity. Sinestro and his group manage to separate Kyle from Ion and then use the Parallax entity that had corrupted and turned Hal Jordan into a villain to corrupt and turn Kyle Rayner into a villain! They take Parallax to their new headquarters, on the planetary attack device now containing their central power battery– Warworld!
Hal Jordan, John Stewart and Guy Gardner travel to rescue Kyle, but are themselves captured, with Jordan sent to Sinestro and his allies. Ultimately, they are rescued by the remaining members of the Green Lantern Corps and they discover that Sinestro is also in league with a resurrected Anti-Monitor! At this point, Hal realizes that Warwold is on route to the Milky Way – Sinestro's main target is the planet Earth!
Hal manages to free Kyle from the control of Parallax, and the pair head for Earth.
The Guardians of the Universe take this time to determine a few important things. First, they determine that the Daxamite Green Lantern, Sodam Yat, will be the new bearer of the Ion entity. Next, they will for the first time amend the Book of Oa! Their first change – Green Lanterns can now use lethal force!
The ability to use lethal force makes a significant difference in the Green Lanterns battle against the Sinestro Corps, and soon they have most of the Sinestro Corps under control. The more pressing problem is Superboy Prime and the Anti-Monitor, not to mention Sinestro himself!
The final battle takes place in “Green Lantern” #25.
Sodam Yat, with aid from most of the superheroes on Earth, fights Superboy Prime to a standstill, but ultimately one of the Guardians sacrifices his life energy to propel Superboy Prime to another dimension.
Guy Gardner and John Stewart manage to destroy Warworld and the central yellow power battery, and the ensuing explosion destroys the Anti-Monitor, as well.
In Coast City, Kyle and Hal (with an assist from the people of Coast City) defeat Sinestro and arrest him. At the close of the war, we learn another effect of the change to the Book of Oa – before the change, Sinestro would have just been sent to prison, but now that lethal force has been authorized, he is to be given a sentence of death!