Natsu Dragneel vs. Alok

Natsu Dragneel vs. Arlock is a fight fought between the former Mage of then-disbanded Fairy Tail, Natsu Dragneel, and Arlock of Avatar.

Prologue
After finding out that Gray has abandoned Juvia and mysteriously left for an unknown place, Natsu, Lucy and Happy continue their quest of rebuilding Fairy Tail and head to Sabertooth in order to discover something about the Ice Mage. There, Natsu stops Rogue just in time to take on his mission of destroying Avatar and the group heads to the cultists' base.

An attempt to infiltrate the building doesn't end well as Natsu carelessly calls for Gray, alerting the members of Avatar and eventually Gray himself, who appears in front of his former guildmates. Seemingly fully devoted to the Avatar's cause, Gray and Natsu begin fighting, but, soon, several more Avatar members appear and the Fairy Tail group ends up captured. However, it turns out that Gray is on an undercover mission, working together with Erza in order to stop Avatar's destructive plans. His cover is blown as soon as Lucy is in a danger of being killed by Goumon, as he appears, freezing the cultist and revealing the plan to Natsu, Lucy and Happy. Afterwards, the group heads to Malba City, with Erza and Gray explaining the details to Natsu and others: Avatar's desire to kill all the people of Malba City in order to summon Zeref. They arrive just in time to stop Avatar's main force from hitting the town, effortlessly knocking out the first wave of soldiers. Eventually, Natsu reaches Arlock's location, stating that losing is not an option no matter how many they are against as a response to the soldiers' despair that just a few Mages were able to stop an army of 2000.

Battle
Before taking any action, Natsu questions whether Arlock is the boss of their enemies. The cultist simply responds that Natsu's small team doesn't stand a chance and tells him to leave. He also comments on the Mage's youth, calling it a wonderful thing, however, he claims that all things age until they reach the point of despair. As he is speaking, Arlock raises his staff, swiftly charging Magic into it and firing it as a beam of energy. Much to the cultist-spectators' surprise, Natsu deflects the attack, however, Arlock is already getting his next spell ready, creating several barriers to stop Natsu from charging at the cultist. Natsu is even more surprised that from the other side of the barrier, Arlock's attacks pass through, dodging several more energy-based attacks. He then attempts to break through the wall with sheer force, and even though the onlookers claim the barrier is indestructible, it soon cracks and Natsu gets through. Arlock proceeds creating several more barriers, but to no avail as Natsu destroys all of them, and with his fist set aflame, he knocks Arlock into the ground, causing a huge explosion afterwards.

Even though Arlock is unable to move anymore, he lets out a giggle, which causes Natsu's attention. The cultist then proclaims that the Fairy Tail Mages will lose, revealing that for this day, he has burnt his own face. Natsu doesn't understand the purpose and Arlock continues, chanting the incanation, using the sacrifice of his face as a price to summon Ikusa-Tsunagi. Natsu looks up as the sky begins to get darker, and from the swirl of Magic, a giant foot appears, landing on the ground in spite of numerous Avatar members being present there. Natsu grabs Arlock, yelling at him to stop this as his own men will get killed and Arlock, with a fanatical expression, reveals that this is Operation Purification, the deaths of those who believe in Zeref being the sacrifice that matters the most. He continues laughing, claiming that Ikusa-Tsunagi can't be stopped until he has finished his work, just as the gigantic figure of one of the Yakuma Eighteen War Gods fully appears in front of Natsu and others, with the Fire Dragon Slayer being furious over the cultists' actions.

A gigantic figure of the summoned being then raises his sword and smashes it onto the ground, causing enough destruction for the survivors of that attack to claim that the Earth has been split. Everyone's attention is suddenly focused on the monstrous sword as there is someone climbing it, that person being Natsu. As he jumps onto the monster's horn and continues making his way to the top, an injured Arlock states that a human has no chance against a god of war. Natsu yells out that what Arlock is doing is hurting the members of the cult and Arlock claims that friends are just in a way of one reaching their own and calls Natsu's definition of friends a mere dependence. Natsu argues that these bonds are what allowed him to survive to this day and dares Arlock to look down on friendship any further. Finally, Natsu, on top of the god's head, performs an explosive attack, which Arlock claims to be futile. Recalling Igneel, Natsu exclaims that in order to never lose a friend again, he'll continue to grow stronger, and surrounds his fist with a huge sphere of Igneel's flames, striking the being with an extremely destructive attack that completely obliterates all of the god's body, much to Arlock's shock, as well as Erza's smile, who confirms that Natsu has really gotten stronger.

Aftermath
Upon seeing the gigantic enemy defeated, all of Natsu's friends watch the god crumble with a content look on their faces. The leftovers of Avatar, however, despair over these happenings, with Arlock further expressing his shock. The opinions of other Avatar members on what to do range from intending to continue the operation, to saving their own necks. Before they can take any action, the council's army appears, lead by Gajeel and Panther Lily, much to everyone's surprise. Lucy also reunites with Levy, both wondering about each other's occupations. Meanwhile, Natsu and others still can't get over the fact that Gajeel is working for the council, with Erza even believing that he was Gajeel's twin brother. As the members of Avatar are getting arrested, the group proclaims that the city has been saved and together, they raise their fists, signalizing their victory. Suddenly, they notice Frosch of Sabertooth near them and even though Natsu is visibly angered that Rogue broke his promise, after Gray hugs the little Exceed, Natsu puts a big smile on his face and the onlooking Sting and Rogue join them, with the evil shadow seemingly disappearing from his Dragon Slayer.