SPOILER WARNING: Major spoilers from Image Comics' "The Walking Dead" #156 follow.
Issue #156 of "The Walking Dead" marks a major turning point in the war against The Whisperers, including a major character death. Don't get too excited by that cover art though -- it's not who you think it is.
Just kidding. It's exactly who you think! Maybe Charlie Adlard and Dave Stewart were trying to fool readers with their illustration of Negan holding Alpha in his arms. Maybe they were trying to hint that this is the issue where they fall in love rather than the issue where Negan kills her -- make that beheads her. But take a closer look at that image. Alpha's eyes are hazy under that skin mask; weak and confused. It's very clear that the life is slipping out of her, and Negan's sadistic grin indicates that he's the one holding the knife.
It doesn't go down in the Robert Kirkman-written story quite like you'd expect, though. At first, Negan seems concerned with proving his worth among The Whisperers via a "Rocky"-esque training montage where he carries firewood, slays his first wild boar with an arrow, and takes down two walkers with nothing more than his knife. But just when you think he's adapting to The Whisperers' animalistic ways, he becomes horrified at two of their males forcing themselves upon an unwilling female. As twisted as Negan is, he's always been strongly opposed to sexual abuse (harems are okay in his book, though), and it's more than he can handle.
What follows is a fascinating debate between him and Alpha about their different philosophies in "The Walking Dead's" post-apocalyptic society. As Negan points out, they're polar opposites in many ways. He's someone who wants desperately to feel emotion and can't, while she's someone who tries to suppress hers, but can't. Then, after she tearfully confesses that she let several men in the camp rape her daughter to build up her strength, Negan slits her throat. It's unclear whether that was his plan all along, or if Alpha's outlook on sexual assault pushed him to kill her. Knowing Negan's complexity, it's probably a mixture of both.
"Wait until Rick gets a look at you," Negan utters to Alpha's severed head. Will his (former?) enemy get as much satisfaction out of her death has Negan? And how will this affect the overall rivalry with The Whisperers, which has stretched for nearly two years in the comics? We'll have to wait and see.