Wildfire, by Jordan S Keller

The Rise of a Hero
Jordan S Keller
Ashes Over Avalon 2
Age level: New Adult
Heat level: Fade-to-Black
Genre: Fantasy Scifi Romance
Tropes: Superheroes, enemies to lovers, morally grey villain, slow burn

After getting fired, flame-powered Abigail makes a reckless deal with a villain to get back into the hero world.  Neither of them knew falling in love was part of the deal.