What American actor also known for playing John Winchester on Supernatural, was also in the film Six: The Mark Unleashed?
Jeffrey Dean Morgan: Jeffrey Dean Morgan (born April 22, 1966) is an American actor. Jeffrey Dean Morgan:  He is known for playing John Winchester on "Supernatural", Denny Duquette on the medical drama "Grey's Anatomy", The Comedian in the 2009 superhero film "Watchmen", Jason Crouse on "The Good Wife", and Negan on "The Walking Dead".
i don't know