[Warning there will be spoilers]
Negan’s a horrible human being. Let’s just make that clear. The man has a baseball bat wrapped in barbed wire because ‘just a bat’ doesn’t send the right message. He pummels heads to the consistency of ground beef as a basic punishment, and routinely tortures, threatens, and abuses his followers into cult-like obedience. He is not good people. Not even close.
But there’s a broken logic to how he works, and a decision making process that isn’t far removed from what Rick could have become. Everyone has their own ways of dealing with the world in The Walking Dead: Alexandria chose denial, Hershel and his family favoured isolation, Terminus went with their "you're the butcher or you're the cattle" motto, while Woodbury’s Governor chose a sadistic and secretive, controlling dictatorship. Finally, Rick and co’s role in the show is largely to be us - to make the decisions we like to think we’d make in that situation. Obviously we’d be dead in days.
Compared to the other groups on the show Negan is probably better than both the Governor and Terminus. For all his violence he just wants to keep people alive, despite there being no transgression he won’t brooch to achieve that, creating a brutally unhinged method to his madness. “There are rules for a reason. Nothing matters if you're dead,” he tells Carl in season 7. Negan’s philosophy is built around this idea, making him a sort of brutal anti-Rick. Both are ready to do almost anything for their adoptive family, they just have different methods. Let’s not forget season 2 saw Rick one good rope yank away from hanging a man to protect his group. Something only the death of Dale (who was vehemently against the idea) prevented. If Rick had seen the execution through, who knows how much like Negan Rick could have become? Don’t forget Rick’s three questions either: “How many Walkers have you have you killed? How many people have you killed? Why?” That’s a pretty brutal way to judge people.
You can flip this around too and wonder if Negan could have been another Rick if life had worked out differently. Both The Walking Dead creator Robert Kirkman, and actor Jeffrey Dean Morgan, have spoken about how the zombie apocalypse shaped him. He was always a bully as an abusive gym teacher before the fall (currently being recapped in the Here’s Negan comic). Morgan adds to this, explaining Kirkman’s notes on how he became who he is: “He starts off really trying to help people and save people,” says Morgan, “and when they don’t listen to him and they’re constantly getting killed, he becomes a little bit more brutal in his tactics, I guess.”
So while Negan is evil, his choices, shaped by previous experiences, make sense to him. Under all the murder and psychological abuse he thinks he’s doing the right thing to help people. He kills, a lot, but not indiscriminately. Take his big arrival at the start of season 7. It’s one the most violent and unpleasant things ever committed to TV, as both Abraham and Glenn’s heads are pulped in retaliation for the slaughter of several Saviours. “You don't really think that you were gonna get through this without being punished, now, did you?” he states. However, it’s what comes next that makes it clear just how calculating he is: “I don't want to kill you people. Just want to make that clear from the get-go. I want you to work for me. You can't do that if you're dead, now, can you?”
So he kills two, and only two, because he knows that the most valuable survival resource isn’t guns or water, it’s people. If you have them, then you can always find more guns and water. In his eyes Rick and his group need to be punished for what they’ve done - Negan’s brutal accounting sees a debt that must be paid - but he also sees these people as an asset. They’re not just workers, they’re exceptionally GOOD workers. To survive as long as they have? And to take out so many of his men? That makes them valuable assets not to be wasted.
Here’s a further demonstration of just how scheming he is: he understands Rick is integral to the group's success, hence the extraordinary length he goes to break him after Abraham and Glenn’s deaths. He doesn’t just threaten him, or rough him up, he systematically peels away the layers until he sees the lights go out and knows that he owns Rick, and thus the group. “That is the look I wanted to see,” he crows after forcing Rick right up to the point of chopping off his son Carl’s hand, and relenting at the last possible moment.
For all the violence, you can see Negan’s beliefs more clearly in his desire not to kill. There’s a strong, if warped, moral compass inside that leather jacket. “Pick whoever you want as long as they say yes,” he tells Dwight when offering up one of his many wives. Or there’s the iron punishment - a horrible ordeal where Saviours who break the rules have their faces burned with a hot iron. If Negan is such a brutal murderer then why not just pound the life out of them? The answer is simple: they’re still useful, dead people aren’t. And in a world where so many are one bad day away from cashing in their chips anyway, what sort of threat is more death? So, instead, Negan punishes when he can and kills only when he has to: “There’s always work, there is always a cost. If you try to skirt it. If you try to cut that corner. Then it is the iron for you,” he says before inflicting the punishment on a victim. “But it’s settled. We’re square, everything is cool,” he concludes after it’s done. As far as he’s concerned, the slate is clean.
Nowhere is this perverse morality more evident than when he talks to the treacherous Spencer after his attempt to get Negan to kill Rick and instate him as the leader of their group. “You know, I'm thinking, Spencer. I'm thinking how Rick threatened to kill me, how he clearly hates my guts. But he is out there right now, gathering shit for me to make sure I don't hurt any of the fine people that live here. He is swallowing his hate and getting shit done. That takes guts,” he says full of admiration. “And then there's you,” he continues, “the guy who waited for Rick to be gone so he could sneak over and talk to me to get me to do his dirty work, so he could take Rick's place.”
Spencer ultimately dies not (entirely) because Negan’s evil, but because Negan sees how toxic that kind of person can be in a survival situation. Spencer’s not just a threat to Rick, he’s a danger to Rick’s group and the Saviours in turn. Contrast that to how he treats Carl after Rick’s son tries to directly assassinate Negan. Carl is humiliated and emotionally abused but physically untouched. If anything, Negan tries to groom and educate him in the ways of the new world with a demonstration of the iron punishment, and some fatherly advice. Carl lives as much because Negan respects him and sees something he can use in the future, as he does because of the more immediate concern of losing control of Rick should Carl be hurt.
That’s what makes Negan more terrifying than any straight up murdering monster. He thinks about who to kill. He doesn’t react without thought or swing wildly, he weighs up pros and cons and reaches a decision. It’s not done because he enjoys it (probably), or there’s no other option, or because he’s completely lost his mind. It’s done for clear reasons and to achieve a goal he’s thought through to the end. And that’s terrifying.