He is the leader of the Saviors, a group of survivors who force other groups to give them half of their supplies, or make them suffer severely. One night, the Saviors ambushed Rick and his group after they had set up camp for the night while on their way to The Hilltop. After that, Negan brutally and savagely bludgeoned Glenn to death with a baseball bat covered in barbed wire that Negan called "Lucille". Realizing just how dangerous Negan really is, Rick unwillignly has his group live under the rule of Negan and the Saviors.
In an attempt to kill Negan, Carl infiltrates the Sanctuary, the Saviors' base, but is captured by the Saviors and taken prisoner. Negan tries to bond with Carl while he is held hostage, but it does not work out when Negan makes a joke about the gunshot wound to Carl's eye. When Rick and the group attempt to save Carl, Negan intercepted them and is about to tell them what he has done with the boy when Rick attacks him, only to discover that Negan has done "nothing" to Carl and that he is fine.
While Rick goes on a supply run, Negan goes to the Alexandria Safe-Zone to watch it while he is gone. There, he encounters Spencer Monroe, who tells him that Rick is not a suitable leader for the Safe-Zone and that when Negan kills him, Spencer will take over. Negan feels insulted by this and murders Spencer, saying that although Rick may hate him, he still has guts unlike Spencer, who he believes acted like a coward.
Afterwards, Negan sees the supplies gathered by Rick and demands it all, but leaves it in payment for Spencer's death. While Negan and some of his men are drivng back to the Sanctuary, they notice that they are being followed by Rick and a few others, resulting in a showdown. In the chaos, many of Negan's men are killed and Carl shoots off a portion of Lucille, causing Negan to develop a hatred for him. After Rick and his group are rescued, Negan retreats back to the Sanctuary, where he tells his fellow Saviors that they are the dominant force in the world and that they are going to war.
All Out War
Rick and his army arrive at the Sanctuary, where Rick offers Negan the chance to surrender. Negan then reveals that he kidnapped Gregory and forces him to pledge his (and that of the Hilltop's) allegiance to Negan and the Saviors or be killed. When only eight people deflect from Rick's side, Negan angrily berates Gregory and kicks him off the balcony. When a firefight ensues between Rick's army and the Saviors, Negan rescues Holly from being killed by a zombie and takes her as a hostage, mistaking her to be Andrea. When Negan catches one of his men, David, attempting to rape Holly, he expresses his hatred of sexual violence by telling David "We don't rape." and stabbing him in the neck before telling Holly that the Saviors are not monsters. Negan is then informed that Rick's army has taken one of his outposts, causing him to order his men to fortify the others. He then arrives at the Alexandria Safe-Zone with Holly and when he gives her over, she is revealed to have been killed and already zombified. Negan and his Saviors start throwing grenades at the Safe-Zone and retreat when Maggie and her forces arrive. Before fleeing, the Saviors kidnap Eugene and Negan attempts to force him to make ammunition for the Saviors, but he refuses.
Negan soon comes up with the idea of using weapons smeared with zombie blood in hopes of infecting Rick's army with the virus. When Negan and the Saviors attack the Hilltop, they start slaughtering and infecting residents before Negan sees Rick and has Dwight shoot him with his crossbow. Unbeknownst to Negan, Dwight's crossbow bolts were not infected and therefore Rick is not infected with the virus. Negan is informed that Eugene had escaped along with help from Carson, Amber and Mark, but Negan says he'll deal with them later. When he arrives at the Hilltop to gain their surrender, Negan is shocked to see Rick alive and angrily turns to Dwight. Rick tells Negan to look at him and asks why he is doing this. Negan says he's doing it to save lives and Rick calls him the stupidest person in the world. He then tells Negan that they should coexist together and just when Negan starts to agree with him, Rick slashes his neck with a knife. Rick then tells the Saviors that he will save Negan's life if they leave and never come back. Rick also reveals that the knife he slashed Negan with was not infected. Negan attacks Rick and the army starts to fire on the Saviors. During the fight, Negan manages to break Rick's leg before passing out. Negan awakens in the Hilltop, where he will kept locked up for the rest of his life to see the survivors live life without the threat of Negan.