The other superheroes were able to stop their rivals and previous friends for only one reason only.

The Indigo lantern corps. They were a special kind of Corps. And it was only wielded by a single tribe in the universe. The Indigo Tribe (Indigo-1 was the main wielder of the Indigo lanterns. Abin Sur forced the Indigo lantern into her after Indigo 1 killed his daughter).

Truth to be told, every Lantern had their own uniqueness. The Orange Lantern had only one Lantern Corp known as Larfleeze. His power was that he could construct the people he had killed in his lifetime thus he was a walking army of his own.

The Red lanterns used blood as a form of weapon and their own blood would be replaced by the light of red rage.

But the most unique were the Indigo lanterns as they could easily teleport over space and read any place in the universe. And another power was in front of other Lantern Corps; they could easily add their own power of indigo light with the other corps and provide more power. This helped Hal Jordan and other superheroes to defeat their enemies temporarily.

Only Super Man and his family was able to defeat the Superman of Earth 2 without any help but even then they were very much spent after defeating him. And that was only one zombie superhero.

Indigo 1 with Hal then went on to travel the universe to gather all the Lantern Corps of different corps to band together and stop the Black Lanterns. Whatever was happening on Earth, it was happening the same over the universe. The Black Lanterns were busy trying to make the other Corps as their own by taking their heart away.

Everything was a mess. And after much conviction and deliberation every other Corp decided to come together. Even Sinestro, who had been the lifelong enemy of Hal decided to keep his feelings at bay and agreed to help.

Thus the final fight started at this point. With all the Lanterns coming together for the first time since the introduction of these Lanterns. This was a huge deal in the series as this scene was one of the epic scenes that the series tried to pull off.

Stolen from Royal Road, this story should be reported if encountered on Amazon.

Even Ganthet, the Guardian of Blue Lantern, showed up for this fight.

Meanwhile, in the Coast City, the home city of Hand, a Black Lantern battery rose in place of his previous home. The Black Lantern looked huge. When every lantern corps arrived it was already too late. They used all of their powers together to destroy the Battery but it only ended up making the Battery more powerful and ended up bringing Nekron in flesh for the first time.

This was a nightmare!!

Nekron looked huge with a scythe in his hand. He would easily be denoted as Death Gods as his body looked like he was the Death Gods that many people imagined him to be. The lantern corps had a face of fear now. They had tried everything possible and even used the powers together but it was still not enough.

And if this wasn't enough, Hand used the body of dead Batman. ( This isn't the actual Batman. It's a clone of his which Darksied made during the Final Crisis. At that point nobody knew that he was sent back in time)

Using his body and the connection he had to other Justice League heroes, Hand was even able to make the other superheroes who were once dead as the wielder of Black Lantern. Clark, Diana and other superheroes were soon changed to Black Lantern Corps. The rings were now coming out of the mouth of Hand which was travelling everywhere to choose their new hosts.

Only Barry was able to escape this change as the Lantern Rings couldn't travel through time. Barry travelled through time to 2 seconds into the future thus saving himself and the Lantern Rings couldn't.

This was a failed war by now. Even Clark Kent, one of their greatest weapons, was on the opposite side. There was almost no hope.

It was at this point that Ganthet did something that blew the minds of everyone. He said.

"Hal Jordan, give me your ring."

"Why? We need it to fight the war."

"Just give me!!"

Hal didn't think much and gave him the Ring. Ganthet took the Ring and made a copy of it, just out of thin air without any help from any machines. Whatever he said next shook the core of the Lantern Corps and even the audience who were watching.

"The Blackest Night is a prophecy in the Book of Oa. Since its a prophecy, the Book of Oa always had contingencies against it. Whatever Lantern Rings were made all this time, the Book of Oa made sure that each Battery and each Ring is under the control of the us...."

"The Guardians."