Negan has been cast for the season six season finale. For those of you who have not read any Walking Dead Negan is the leader of a group of over 50 survivors in Washington, DC called the Saviors, who subjugate other communities in the area for resources in return for their protection against zombies.
Several actors could have been considered to play Negan especially Henry Rollins who Negan was based on, but Jeffery Dean Morgan has been cast to play the big baddie.
Andrew Lincoln was asked about Negan "What struck me, that I've always been excited about, is: We're coming into the sixth season of this show. ... And it's the medieval part of The Walking Dead comic, where you realize that there are these isolated communities, but don't really know other ones exist," he also went on to say "But they're all building and forming themselves with their own image. And then there's a clash of those communities. That, to me, is really interesting and when it gets really exciting with all the action. It turns into this insane, near-apocalyptic landscape that we've never seen before. That is almost a reimagining and a restart for society and humanity. And that is such a rich thing to tell."