A/N: The first of my OC Bens. This Ben is the Ben in the Gwen 10 universe.
In almost every universe, Ben Tennyson is the Wielder of the Omnitrix, the Hero of Heroes. In a tiny minority of universes, however, Ben Tennyson doesn't have the Omnitrix. In one universe, Gwen does, and Ben becomes something else. Something alien…
It began after the Time War. Ben felt inadequate when Gwen told him about it, and about all the other alternate Bens she fought with and fought against. It raised questions in Ben's mind. What made him different from the other Bens? Was he stupider? More immature? An ordinary person would assume that they were the one in fault and change themselves. Ben didn't. He blamed Gwen. Gwen was so perfect, she had the Omnitrix, and she could fight. Ben couldn't. He got angrier, and angrier.
Then he exploded.
Not literally, although it felt like it. Light just burst out from his body and he felt like he was flying in starlight. Then he crashed down to Earth and found himself in bed. He didn't know what had happened. Nobody did. It was only when he found Charmcaster's spell book that he realised that what he did was magic. Very powerful magic.
He found out five years later what he was from Grandma. He was an Anodite, an energy being. One of the most powerful aliens in the universe, whose lack of DNA meant that they weren't in the Omnitrix. He had something that Gwen didn't have. Gwen could turn into aliens, but he was an alien.
Then Grandma dropped a bomb-shell. In order to achieve his full potential, he had to leave Earth and go to Anodyne. It was a hard choice. A choice taken away from him when Gwen didn't react fast enough and his human body was destroyed. He managed to stay on Earth undisturbed for a few more months. But after the fight with the Highbreed, Gwen's identity was revealed and she got a team together, a decent team not made up by the Wielder of the Omnitrix and two boys with unstable powers, a good team: Gwen's Team. Ben didn't think he had a place on that team. He made his choice. He went to Anodyne.
Ben stayed on Anodyne for almost two years – or at least, he thinks it was two years, time worked differently on Anodyne – before he got a message from Grandpa Max. Gwen had given up crime fighting to go to college and they needed a defender on Earth. The Plumbers weren't enough. They wanted a true hero. Ben agreed. He made a new human body for himself, exactly like how he thought he would look like at eighteen, and went to Earth. He felt…trapped in his human skin, like it wasn't him. He missed being able to be free without the confines of skin. He wanted to be free.
But he had a duty, and Grandpa Max was counting on him. He went to Earth.
Earth suddenly felt small, alien, like he didn't belong there. Which, Ben supposed he didn't belong on Earth anymore. He wasn't human. He was an Anodite. He was the alien. Even when compared to Rook, he was more alien despite having been human once. He stayed there just long enough for Gwen to finish college. Then he left. Earth wasn't home anymore.
Returning to Anodyne, he also felt like Anodyne wasn't home. He missed helping others, seeing the universe. So he left (with Sunny, who insisted on joining him). He travelled the universe, became a protector in his own way. People loved him, they respected him. He was powerful, his abilities were matched by no other. They relied on him. He felt needed.
He returned to Earth only once. Twenty years had passed and Gwen was going obsessive over the Omnitrix and defeating bad guys. Ben helped Kevin calm her down, telling her she could take a break. The Galactic Enforcers could take over every so often, so Gwen could rest. He didn't even return when Gwen gave birth to Devlin, although Ben felt like he was missing something when Gwen sent a message about having a son.
Still, Ben was content in space. Becoming what he always wanted to be: a hero. A true alien hero.
A/N: I got this idea from when I watched Showdown: Part 1 and wondered 'why does Ben like Feedback so much'. Then it hit me. Feedback is a Conductoid, he feeds on energy. Anodites are pure energy. Ben's Anodite side was absorbed by Feedback and then lost when Malware destroyed the transformation. Ben literally lost a piece of himself when he lost Feedback. It also explains why Ultimate Ben in Ben 10,000 Returns can use Anodite magic despite not being an Anodite, because he is an Anodite, he just can't become an Anodite's full potential because he lost that side of himself.
The reason why Ben doesn't care about Earth any more is because his humanity was destroyed when Verdona destroyed his human body. Ben doesn't like Verdona very much because of this.