John DeMarco

John DeMarco is a minor villain found in Batman: Arkham Origins - one of several criminals Batman tracks down in side-missions and while not a necessary part of the game nor a pivotal part of the main storyarc is still an antagonist to be found in Gotham's dark and violent underworld of gangs and corrupt police officers.

a member of Gotham's SWAT team John DeMarco was not only an aide in Branden's corrupt dealings with the force but also a cold-hearted killer who engaged in a hit-and-run vehicular murder of Nate Ramo, a fellow member of the SWAT team who had decided to come clean with IAD about some of trhe team's corrupt dealings - this angered DeMarco sufficently that he took it in his own hands to kill off the "traitor".

Batman would use his detective skills to gather evidence at Ramo's murder scene then pursued DeMarco to a nearby location where the Dark Knight confronted DeMarco on his misdeeds, however DeMarco was not scared and warned Batman that evidence had a "funny way of disappearing" : Batman in turn warned DeMarco such evidence would not go missing on "his watch" and knocked the criminal out, for collection by authorities off-screen.