The Puzzle of the Talking Dinosaur — Warren Bluhm

At some point in the life of a superhero must come the first encounter with the most evil of evil villains, the nemesis of nemeses, the bad guy above all bad guys, and in the case of Myke Phoenix, the time has come to meet Deinonychus, the ruthless and impossible being behind most of the bad stuff that happens in Astor City. After she murders her top underling in a courtroom and reveals his unexpected vulnerability, the city's superpowered protector must track her down before she can strike again - or die trying.