Renegades by Marissa Meyer

Secret Identities. Extraordinary Powers. She wants vengeance. He wants justice.

The Renegades are a syndicate of prodigies — humans with extraordinary abilities — who emerged from the ruins of a crumbled society and established peace and order where chaos reigned. As champions of justice, they remain a symbol of hope and courage to everyone... except the villains they once overthrew.

Nova has a reason to hate the Renegades, and she is on a mission for vengeance. As she gets closer to her target, she meets Adrian, a Renegade boy who believes in justice — and in Nova. But Nova's allegiance is to a villain who has the power to end them both.