Harley Quinn could also be a great character for Terry to interact with. She has a complex personality. In the Injustice universe, she's been through a lot. Terry might be initially suspicious of her, but as they interact, he could discover that there's more to her than meets the eye and that she could be an ally in his attempts to restore justice.
Batman from the Injustice universe himself could be a fascinating character for Terry to interact with. They are both Batman in different ways. The Injustice Batman has endured so much and made some very tough choices. Terry could learn from his experiences and perhaps offer a new perspective on how to deal with the chaos in the Injustice world.
Superman would be extremely interesting. In the Injustice universe, Superman has become a dictator of sorts. Terry, as Batman Beyond, represents a different kind of heroism. Their interaction could be a clash of ideologies. Terry would likely be appalled by Superman's actions and try to make him see reason, which would lead to some intense and thought - provoking exchanges.
Batman Beyond would be the most interesting. He's a new take on the Batman concept with his high - tech suit and different personality compared to the original Batman. He has to prove himself to the Justice League and show that he's just as capable, if not more so, in his own time.
One idea could be exploring an alternate universe where Terry McGinnis (Batman Beyond) is pulled into the Injustice universe and has to deal with the morally compromised heroes. He might try to find a way to bring back the true sense of justice among them. For example, he could start by trying to reason with Superman, showing him the error of his ways through his own experiences in his own universe.
Robin, in all his incarnations, is also a popular character in fanfiction related to Batman. He represents the sidekick aspect and the growth and development that comes with it. In Batman Beyond, Commissioner Barbara Gordon also features prominently in some fanfictions. Her connection to the original Batman era and her role in the new one can be explored in interesting ways.
Definitely Terry McGinnis. He's the central figure in Batman Beyond and in fanfic, his story can be told in so many different ways. He has to balance his normal life as a teenager with his superhero duties. Then there's Inque. She's a really cool and unique villain in the Batman Beyond universe. In fanfic, she can be made even more menacing or given a more complex backstory. And let's not forget Brother Eye. It's a super - interesting concept that can be explored in great detail in fanfic, adding new layers to the Batman Beyond world.
I think Superboy would be really interesting. In Young Justice, he's still finding his place and dealing with his Kryptonian powers. In the Injustice universe, he'd be faced with a very different version of Superman. He could be a bridge between the two worlds, trying to understand the darker side of power that the Injustice Superman has embraced while also holding onto his own ideals from Young Justice.
Batman himself is obviously very popular. He's the central figure and fans love to explore different aspects of his character in this 'injustice for all' scenario. His intelligence, combat skills, and unwavering sense of justice are always interesting to write about.
Batman would be the most interesting. He doesn't have superpowers like the Avengers, but he's still a formidable hero. His presence in their world would be like a wild card. He'd be constantly analyzing the Avengers and their enemies, and his dark, brooding nature would contrast with the more flashy and super - powered Avengers.
Terry McGinnis is definitely one of the most interesting. As the new Batman, his character has a lot of potential for different relationship dynamics. He has his own set of challenges and a unique backstory that can be explored in various relationship scenarios. Another interesting character is Max, Terry's friend. Her relationship with Terry can be developed in interesting ways in slash fanfiction, whether it's a romantic or a very close platonic bond. And then there's also the villains like Blight. Writing about his interactions with Terry or other characters in a different light can be really engaging.
Superman would be really interesting. Their powers are quite different. Superman is an alien with a wide range of powers like flight, super - strength, heat vision etc. The Hulk, on the other hand, is a being of pure rage with ever - increasing strength. Their encounter could be a clash of ideologies as well. Superman stands for truth, justice and the American way, while the Hulk is often just a force of destruction when enraged. It would be fascinating to see how Superman tries to calm the Hulk down or how the Hulk reacts to Superman's attempts at peacekeeping.
Batman Beyond and Wonder Woman would also be an interesting combination. Wonder Woman's warrior - like nature and her connection to ancient mythology could be an interesting foil to Terry's futuristic, urban - based crime - fighting. They might team up to stop a threat that combines both ancient magic and modern technology, like a villain using an ancient spell to control high - tech weapons.