Board Thread:Mortal Kombat X/@comment-1354446-20150425075956/@comment-21005855-20150429044456

Not a bad theory but I don't think that's why he's dark. He sacreficed himself to cleanse the Jinsei, which was corrupted. After that, we skip on to the end when Raiden visits Netherrealm with the head of Shinnok. I think it's the cleansing process that Raiden did that corrupted him to become Dark Raiden.