Generally when you think of a district attorney and comic books, you think of Two-Face aka Harvey Dent/Kent, the Earth-One/Two D.A. whose face was scarred leading to his tragic career as a criminal.
Two others sought a different path than their traditional career, due to tragedies they each faces. Adrian Chase lost his family due to the vengeful gangster, Daniel Dyce took the place of a criminal who wanted to see the birth of his child. When Adrian was left with nothing but grief he assumed the identity of Vigilante, and when Dyce's crooked clone died at the hospital Daniel ended up taking his place as prisoner #711.
Each man evaded the law enforcement authorities they once were employed by in order to bring criminals to justice, Vigilante for his brutal form of justice and 711 for escaping prison (although no one seemed to realize it at the time). Both ended up perishing during cases avenging the crimes of the wicked whom they faced over and over again.