After some time had passed, Cloud was going to be able to return to Nibelheim for the first time since his departure. When he, Zack, Sephiroth, and another Shinra MP enter into the town of Nibelheim, Cloud quickly notices Tifa. In order to hide the fact that he didn’t join SOLDIER, Cloud goes to put his helmet back on. The group is here on a mission to take care of the monster outbreak near the Nibelheim Reactor up on top of Mt. Nibel. Sephiroth allows everyone to go visit the town before they head up to the reactor. Cloud, of course, goes home to his mother for a visit. However, he does not look for Tifa; he would prefer to not show himself to her, in fear that she would consider him a failure—after all, he had already considered his own self a failure for not making SOLDIER. The next day, Sephiroth, Zack, and their guide to the reactor—this is Tifa, by the way—along with two Shinra MP’s head up the large mountain. Along the way, the bridge to the reactor breaks while the party crosses and one of the MPs is killed by the fall—this is not Cloud, but the other random MP who decided to come with them.
Eventually, they reach the reactor and Sephiroth, along with Zack, enter into the building while Cloud stays outside to make sure that Tifa doesn’t enter and is kept safe. Inside, however, things are getting quite intense. Sephiroth is realizing that he was an experiment, that he was different from everyone else. He storms out of there and locks himself in the Shinra Mansion for a long while—the light in the basement is said to never go out. Zack enters into the Mansion, but to find that Sephiroth has changed completely. He begins ranting about Jenova, claiming her as his mother, and says that humans are traitors. In all his hatred, he burns Nibelheim and kills many of the people of its townspeople. Shinra MP, Cloud Strife, is seen passed out near his house and Zangan is seen helping the live victims. Zack also comes out of the Mansion to see the fire; he quickly rushes over to Zangan to see what has happened. He tells him that Sephiroth went to the reactor, with Tifa chasing after him—he quickly makes his way there to confront the enraged Sephiroth.
Cloud eventually awakens from his dazed state and also quickly rushes toward the reactor. By the time he arrives, Zack has been badly wounded and Tifa is lying in the middle of the floor after trying to attack Sephiroth herself. He moves her out of the way and comforts her. She tells him that he came during her time of need; the hero she had always wanted to rescue her when she needed it, Cloud was the one who fulfilled his promise. Despite thinking he was a failure and that Tifa would be ashamed of him, he still fulfilled the promise he made to her many years ago. Angrier than ever, Cloud takes his friend—Zack—Buster Sword and heads into the room where Sephiroth entered. Cloud not wasting any time runs toward Sephiroth and stabs him directly in the back—piercing all the way through him. He then gives a few choice words, reinforcing his statements to Tifa as a child: He had admired Sephiroth.
Sephiroth: “Aaarrrgh… who… who are you?”
Cloud: “Mom… Tifa… my town… give it back… I had so much respect for you… admired you…”
Sephiroth, still alive, manages to take Jenova’s Head and exits the room on his way out of the reactor. However, Cloud chases after him, when he gets within the range of Sephiroth’s Masamune, the silver-haired warrior turns and stabs Cloud right through the chest. Cloud, using all of his remaining strength pulls the sword through himself more, gets a solid grip—his hands bleeding from the swords sharp edge—and thrusts Sephiroth over the edge into the Mako below, along with Jenova’s Head. Cloud… the same Cloud who had so long wanted to be strong, so long wanted to have confidence in himself and for the one he so deeply cared for to pay attention to him, had defeated the greatest soldier to ever live.