By its ending, it becomes clear that series' most charismatic antagonist, Negan.
Stretching over 193 chapters, The Walking Dead begins with Rick to change the fascistic Commonwealth, effectively saving human society from returning to its worst impulses.
Strangely, Rick sparing Negan and redeeming the Commonwealth is actually foreshadowed by his very first zombie kill. In The Walking Dead #1 - from Robert Kirkman and Tony Moore - Rick awakes from a coma and escapes a zombie-filled hospital. Stumbling out onto the road, Rick discovers an injured zombie which is aggressive but unable to move. After meeting some survivors and arming himself at the local police station, Rick is warned not to waste ammunition on zombies who aren't immediate threats. Nevertheless, before setting out to find his family, Rick revisits the injured zombie and shoots it, shedding a tear before moving on.
What's notable about this kill is that it clearly comes from a place of comion. Rick sees the zombie suffering and - despite having already been attacked by the undead - resolves to put it out of its 'misery.' The moment shows that no matter how horrifying the enemy, Rick is able to access a sense of comion and even to sacrifice things he needs to prevent what he perceives as suffering.
This trait doesn't always win out in The Walking Dead - Rick gives in to hatred several times when faced with human depravity - but it's core to who he is. Later, when Negan is defeated and at Rick's mercy, Rick opts to guide his burgeoning society in the same direction, choosing the hard work of rehabilitation over the easy satisfaction of revenge. While it's clear that Rick doesn't forgive Negan, he's able to overcome his baser instincts in favor of the choice he thinks will foster a meaningful sense of humanity in his group of survivors. Ultimately, this choice changes the future of the human race, as Rick's way of thinking is ultimately embraced by the Commonwealth.
Rick's example in showing mercy to Negan permeates society. The final issue of Walking Dead sees Negan voluntarily exiled from society, processing his grief and guilt, while Rick's own killer is incarcerated despite slaying a hero who has grown to mythic proportions. The Walking Dead #1 presents Rick as someone who goes out of his way to prevent suffering and embrace dignity and comion, even when there's no-one around to see it. While the story plays with the idea that the horrors of the world will strip Rick of this outlook, this isn't the case, and the example he sets dictates Negan's final fate, as well as making the human civilization that survives The Walking Dead's apocalypse one worth living in.
