Wally could be developed by showing his growth in character. For example, if he was a bit cocky before, he could return more humble and with a deeper understanding of the world. This change could be a result of his experiences while he was away.
Well, it could be that Wally returns with new superpowers. Maybe he was in some sort of time - warp or alternate dimension and comes back stronger. He might have to prove himself to the team again that he's still the same Wally they knew.
One idea could be that when Wally returns, he has new superpowers. Maybe he gained the ability to manipulate time during his time away, which he has to learn to control. This could add a whole new dynamic to the team as they deal with the implications of such a powerful ability.
In a 'Young Justice Outsiders Wally Returns' fanfiction, he might return as a changed person. He could have lost his memories while away and slowly regain them as he interacts with his old friends. His return could also bring back old threats that were thought to be gone. For example, an enemy from his past might resurface, believing that Wally holds the key to something they want.
Maybe a villain from the dimension where Wally has been. This villain could have followed Wally back to seek revenge or to take over the world that Wally has come back to. Since Wally has some knowledge about this villain, it would be his responsibility to stop the villain and protect his friends and the world. The villain might have powers that are a match for Wally's, making it a really tough fight.
Yes, there are quite a few. Some fanfictions show Wally West with enhanced speed powers or unique abilities that set him apart even more in the Young Justice universe. They often explore his character development in ways the show might not have had time for.
One great 'Great Wally West Young Justice' fanfiction is 'Speedster's Redemption'. It delves deep into Wally's character, exploring his growth after facing some tough challenges in the Young Justice universe. The author does a wonderful job of capturing his voice and the relationships he has with the other characters.
One great fanfiction could be about Wally West getting some unexpected training from Doctor Fate. Maybe Fate sees potential in Wally's speed and decides to teach him some magic - related skills to enhance his combat abilities. This could lead to some really cool adventures where Wally has to combine his super - speed with new magical powers.
It could be a new villain who has a vendetta against speedsters. Since Wally is a speedster, this villain might see his return as an opportunity to prove himself. Maybe he's a scientist who has developed a weapon specifically designed to counter speedsters' abilities.