For the longest time, the Governor was the worst of the worst in THE WALKING DEAD universe, up until Negan came around. Today, it was announced that Jeffery Dean Morgan (The Losers) has been tapped to fill the role of Negan, according to THR.
The character will make his debut on the season six finale of the show. In the comics, Negan was the leader of The Saviors, a group of survivors that used violence and intimidation to get what they wanted from the surrounding areas. Negan first showed up in issue #100 of the comic, in the most memorable way possible [seriously spoilers] by beating Glenn to death with his baseball bat covered in barbed wire, which he named Lucille.
Showrunner Scott Gimple had this to say about Negan appearing on the show.
There's a particular story in that arc that I'm very excited for. But because we know where we're going, we have some opportunities to play around with it and put some things in that will lead up to [Negan and Alexandria] in different ways yet fulfill the story Robert told to the Nth degree by utilizing some slightly different approaches. Lineups and timelines and the whole nine yards.
Because of what's happening on the show, it's hard to know if Negan's entrance will remain true to the comics or if the showrunners will go another way. However, it will lead to an All Out War and one of the biggest battles in the comic book's history.