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Manganiello was at Oz Comic Con in Melbourne, Australia this weekend. According to a fan on reddit, who says he was in attendance, Manganiello said that Ben Affleck and Geoff Johns were working on The Batman script which included the villain Deathstroke. Former DC Films head Jon Berg Googled “Deathstroke”, saw some fanart of Manganiello in the role, and they made the call.

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