John Constantine is a fictional character.
An antihero , or antiheroine , is a protagonist who lacks conventional heroic qualities such as idealism , courage , or morality . Constantine is an American television series developed by Daniel Cerone and David S. Goyer for NBC , featuring the DC Comics character John Constantine . John Constantine . Welsh actor Matt Ryan was cast in the role of Constantine for the 2014 NBC television series Constantine , a role he reprised on The CW series Arrow , the animated film Justice League Dark and is set to reprise again in an upcoming animated continuation of his series on CW Seed . The Swamp Thing is a fictional character in the DC Universe .