One Piece's Straw Hat Crew encounter many eccentric and peculiar villains throughout their sea-faring adventures. When their journey took them to the Knock Up Stream into the Sky Islands, they faced off with the Thunder God Enel and challenged his tyrannical control of Skypiea. In his defeat at the hands of the rubber pirate Monkey D. Luffy -- who had the perfect counter to his lightning Devil Fruit the Goro Goro No Mi -- Enel sailed the skies on his ship, the Ark Maxim, toward Fairy Vearth to achieve his dream.
Recent manga chapters have seen some significant developments regarding the nature of Luffy’s Devil Fruit, originally believed to be the Gomu Gomu No Mi, a paramecia that gave him the qualities of rubber. However, it was revealed to actually be the Hito Hito no Mi, Model: Nika, a Mythical Zoan for the Sun God, Nika. This Sun God Nika was foreshadowed in the "Skypiea Arc" during Chapter 253 and later in Chapter 300. The silhouette Luffy formed in the fire celebrations resembled the imagery shown during Who’s-Who’s description of the Sun God Nika during the invasion of Onigashima. The return to vital plot developments during the "Skypiea Arc" could lay the groundwork for Enel to return to the story.
Where the One Piece Manga Left Off With Enel
The pseudo-God Enel has remained absent in One Piece since his departure to Fairy Vearth, more commonly recognized as the Moon. He was given a mini-arc to show readers his adventures on Fairy Vearth, depicted on the chapter's cover pages. After battling Space Pirates, reanimating small automata animal warriors and learning the history of the Sky People through hieroglyphics painted on a wall, Enel took his place as the God-King of Fairy Vearth and established his rule over an army of robots.
As Enel and Luffy’s confrontation occurred before the time-skip, Enel has been enjoying his unchallenged reign for over two years. He may be content with his position on Fairy Vearth, only needing to absently crush Space Pirates should they invade his kingdom or use his lightning to recharge the automata when they run low on power. In fact, Enel has shown to be the type of man who believes himself to be immortal but is also lazy due to his entitled nature. Being worshipped by a sect of people, even if they are robots, might be enough for him to live out his days in his own personal bubble of luxury.
Enel May Still Have a Crucial Role to Play in One Piece
The more prominent antagonists in One Piece have made some sort of return to the story after their defeat. Buggy and Crocodile helped Luffy in Impel Down and the former became a Warlord of the Sea. More recently the Captain of Grand Cross, Bellamy, became an admirer of Luffy and turned on his Captain for the rubber menace. Rob Lucci was promoted to CP0 and appeared in Mary Geoise, Doflamingo has been shown a few times in chains, though has a connection to the developing plot with the World Government.
In the case of Katakuri, Big Mom, and Kaido, it is too early to see if they have a bigger part to play in the story's grand scheme. As Enel was the main antagonist of the "Skypiea Arc", there should be a place for him in the closely arriving conclusion of One Piece.
Even with the inclusion of Haki into the story and the Straw Hats' increased power levels, Enel is still a considerable threat. His Devil Fruit’s destructive capabilities are beyond many others that came after. That said, it is unlikely he would return just to seek a conflict with Luffy; it is far more likely he will have learned the history of his people on Fairy Vearth and perhaps some details concerning the Sun God Nika -- whom the Sky People were said to worship -- that could be relevant to the One Piece. If a man such as Crocodile could see the benefit of siding with Luffy, it is not impossible for Enel -- even if it's a bit more challenging with his God complex. The connection with Skypiea and Luffy's Devil Fruit has been foreshadowed; who better to unveil some of this mystery than an antagonist who has access to the Sky Islands' history?
As the Straw Hats Fleet is ever-growing and their allies increasing, the introduction of a Thunder God and his army of automata space warriors could be what they need in the series' final conflict. While Enel is not the type of man to help the Straw Hats out of personal responsibility or a feeling of guilt for his actions, neither was Crocodile. If there was something that could be gained from ensuring the Straw Hats victory over their final threat, Enel would mercilessly toss his army of robots into the fray and bombard the battlefield with El Thor to make it happen.
Ultimately, it is unlikely Enel has grown as a person in the two years spent on the moon, but not impossible. Eiichiro Oda created a world of surprises with One Piece, and a bigger surprise than Enel having a change of heart would be hard to come by. In the end, the final saga will reveal if there is a place for him -- but seeing the self-proclaimed God riding the Ark Maxim down into a final war would be a sight to behold.