It's no secret that Negan has earned the wrath of numerous characters in the comic, as well as many fans. Since his introduction, there's been much speculation over which character will get to kill him (which, for the sake of the story, I hope is very far off). I've heard theories that either Rick, Carl, Maggie, or even Dwight will get to kill him. While I don't object to these theories or any others necessarily, I believe that the one character who deserves to kill Negan the most is Sophia, for several reasons.
Despite having been in the series since nearly the beginning, as well as being the longest surviving female character of the series, Sophia has been largely sheltered from the harsh conditions of the apocalypse. That isn't to say that she hasn't suffered her share of losses, having lost both of her parents and adoptive parent, but rather than adapt to these harsh conditions the way carl has, Sophia has gone to great lengths to hide from them. When her mother committed suicide, rather than facing it or at least talking about it, she imprinted on Maggie and Glenn in order to maintain the illusion of having never lost anyone. Indeed, the idea of those closest to her taking their own lives has been a fairly constant theme in her life. Her father killed himself as did her mother, and her adoptive mother very nearly took her own life at one point.
This distinguishes her from other child characters such as Carl or Clementine, in that while both of them lost loved ones to violence, her loved ones abandoned her, or at least tried to at some point. Yet not only has she never allowed herslef to grieve over these events, but the adults in her life enable her to remain emotionally constipated over these issues. While they shouldn't constantly remind her of her losses, having a serious discussion about them with her so that everything she's suppressing won't come to a boiling point is preferable to endulging her state of denial. Not everything that needs to be said is easy or pleasant. Even taking that aside, few if any adults have gone to great lengths to prepare her to defend herself if need be. While Carl is not exactly an icon of psychological health, Rick has never failed to impress upon him the seriousness of their situation or the necessity of being prepared. Because of this, Carl has survived through his strength of will and overall competence. Sophia, on the other hand, has always surrounded herself with those who could protect her, never having once been forced to kill anyone living or dead.
Arriving at the center piece of this blog, the introduction of the Safe Zone offered a return to relative normalcy that for a while seemed to make adapting to the apocalypse irrelevant. Yet even when this illusion of safety was shattered beyond repair, Sophia still had Maggie and Glenn, and even nonchalantly acknowledged at one point that they were not her real parents, not as a way of hurting them, but to alleviate their concerns over her mental state. This milestone was short lived however, as not long before she was promised a new beginning with a new family, as well as a new sibling on the way, Negan quite literally shattered any possibilty of that right in front of her. With that, the one family member she had who never once considered abandoning her was killed, at random no less. Shrotly afterward, for the first time in the series, Sophia actively fought in defense of someone she cared for, against Carl no less. The level of aggression she displayed in that moment is surely indicative not only of emotions that have built up for a long time, but of things to come.
In summary, killing Negan would not only be a source of tremendous poetic justice, but it would provide the best opportunity for a long enduring yet largely underwritten character to achieve her full potential, thus validating everything she's endured up to this point.