Well, Barry Allen's powers came about due to a freak lab accident. Lightning struck a shelf of chemicals, and the combination of the electricity and the chemicals bathed him, granting him super-speed abilities.
Well, Barry Allen acquires his powers during a freak incident in a laboratory. Lightning struck a shelf of chemicals, and he was doused in the mixture, which granted him his amazing speed capabilities.
Perhaps he gets a power related to mind control. This would allow him to influence the actions of his enemies or even make them fight among themselves. He could also gain a power that lets him absorb the powers of his defeated foes. So, every time he defeats an enemy, he becomes stronger by adding their powers to his own arsenal.
One possible scenario could be that Barry gets hurt during a fight with a powerful meta - human. Maybe the meta - human has some sort of energy - based attack that Barry can't dodge in time, and he gets severely injured. Another scenario might be that he gets hurt while trying to save someone from a dangerous situation, like a collapsing building or a runaway vehicle. In some fanfictions, he could also get hurt due to some sort of betrayal within his team, where someone accidentally or purposefully sets him up to be attacked.
If Supergirl and Barry are in a relationship in the fanfic, their powers could interact in some interesting ways. For example, Barry's super - speed could be used to enhance Supergirl's combat abilities. He could quickly move her around the battlefield, allowing her to surprise enemies. Supergirl's strength could protect Barry when he's vulnerable during his high - speed runs. They might also combine their powers to create a sort of 'super - blast' by having Supergirl charge up an energy attack while Barry spins around her at super - speed to amplify it.
Obviously, Dipper is the main character as the title implies. His sister Mabel is often included too. She might react in various ways to Dipper getting powers, like being excited or a bit jealous. Wendy is also a common character. She could be a source of support or a love interest for Dipper in some fanfictions.
In this fanfiction, Robin might get powers as a result of a genetic mutation triggered by a rare chemical. These powers could include enhanced speed and the ability to see in the dark. He initially hides his powers from the team because he's afraid of how they'll react. But when a dangerous situation arises where his powers could be the key to victory, he reveals them and they all work together to defeat the enemy and accept his new status.
Well, it could be that Naruto gets some kind of elemental powers from the comet. Maybe the comet is associated with a new, rare element that Naruto can then manipulate. This new power could give him an edge in battles, as his opponents would be unfamiliar with it. He could use it in creative ways, like combining it with his existing jutsu to create even more powerful attacks.