Carlos aka Boulder was at the base with Rahul's team, thinking over Rahul's proposal while, Slither, another lieutenant of Cronos was still out wreaking havoc in other areas. It was Sly whom Carlos fought and almost defeated before getting knocked out, and Rahul's team taking over and defeating Sly.
Carlos was in great confusion whether to accept the offer or not because of Abhimanyu, who was the guy who wanted to catch him for his deeds, whereas Abhimanyu had forgotten about what Carlos did in the past, all he was thinking about was what he could do now alongside of his powers. Carlos was very confused, but he concluded after some time that he would assist Rahul and his team to fight these invaders and to protect the earth, because of his own greed.
Now with Boulder on his side, Rahul can imagine how to defeat Cronos and his lieutenants. In the meantime, Rahul is getting more powerful day by day. He can now do feats that he never had done before, he can now be invincible by changing the molecular biology of his body. He can be extremely strong and at times he can be extremely lethal. He could also change his size now, going straight from giant to atomic size. He can also control the surrounding area's atomic makeup.
Together they faced Slither and easily defeated him to bring out Cronos. As the result Cronos himself came to confront the Legion. The Legion on other hands were ready for what was coming. Cronos did come to earth but not alone, with him was another two lieutenants, Smokescreen and Blackout. Both had ability to control light, either make it dark like pitch black so no one can see anything or make it too bright so that no one can withstand it. In the cases they remained unaffected. It was on Quantum King to figure out what to do.
On other hand Cronos had already brought his wrath upon the planet. Between him and planet earth lies only one hurdle and that is the Legion of Superheroes. Soon both sides had indulged in fighting each other. Both Smokescreen and Blackout were causing trouble to the Legion, beating the crap out of them. Quantum King tried to control the smoke created by Smokescreen, but he can't control all of it. Blackout was more powerful than Smokescreen as she can control all forms of light while Smokescreen just created clouds of smoke to block light. Eventually Smokescreen got defeated by Crystal and Shadow, others were still busy fighting Blackout.
After several attempts to defeat Blackout being gone into vain finally Quantum King defeated her. Using his quantum powers Quantum King created a high-density high gravity void around her through which even light could not pass through. This caused Blackout to collapse in it. After all this they headed for Cronos himself. Defeating Cronos wasn't an easy job after all. In the fight Dark Flame got killed and Shadow was injured severely. With all their effort they did defeat Cronos. Dark Flame sacrificed himself to save Boulder and Crystal. Finally, Quantum King along with Boulder and Crystal defeated Cronos by making him run into the trap which he created to capture Cronos. Boulder used his powers to hold Cronos's feet, while Crystal used her telekinesis to hold tight Cronos's body while Quantum king used his quantum fist along with his atomic spear phasing right through Cronos's heart.
After all this Boulder did realized that Dark Flame did cared for him. All returned to their lives. Maya aka Crystal finally became the superstar she wanted to be. Carlos aka Boulder did return to his normal life only things that have changed are that he had quit robbing and has started his own security company which also has security contract of Rahul's aka Quantum King's father's company. Pratik aka Shadow is being treated in London. Rahul is now living with Jane and has finally accepted her marriage proposal.
Rahul and Jane were married few months later and a couple of years later they were having a girl together whom the named Lilly.