Carl Grimes has a destiny to fulfill according to Negan, who claims the boy is a future serial killer. Living in the apocalypse with Rick as a father and Shane as a life coach, not to mention the zombie apocalypse that is swarming around him 24 hours a day, has perhaps made this prediction take weight and grow legs. Most people wouldn't take the bet in Las Vegas that Carl is going to grow up well adjusted. No one is well adjusted in the apocalypse.
No longer an innocent boy
When other boys like Patrick were spending their free time assembling Lego bricks, Carl was disassembling, cleaning and repairing guns. All of this was in preparation for the short-lived war with the Governor, who in hindsight doesn't seem like such a bad guy compared to Negan and the cannibals at Terminus.
What Carl has lived through, and survived, is what is going to make him stronger even if it's at the loss of his innocence. Rick has tried to protect his son during the downfall of humanity, but there's only so much a man can do to shield his family from the brutality of nature.
Three father figures, two mother figures
There was a time when all Carl had left for a father figure was Shane Walsh, his dad's partner and the guy who was sleeping with his mom when all hell broke loose and the zombies attacked. The strange duality of parenting that existed once Carl's real dad showed up took life changing measures time and again. Shane, a brutal antagonist who delivered fearless death upon his enemies, taught Carl to shoot and be feared. Meanwhile, Rick taught Carl important lessons about his future moral compass and how to tame a wild heart. Now that Negan has arrived, it's almost as though Carl has a third father figure, and this was evident when the unusual pair spent an episode together this season and began an uneasy friendship based on mutual fear and respect.
What could be interesting in the future is if we see Michonne continue down a path towards being the closest thing Carl has seen as a mother figure since Lori Grimes died during the birth of his sister, Judith Grimes.
An uncertain future of fear and hope
Now that Carl and Enid are headed towards something that resembles a relationship, he's taking the first step in enlarging his small circle of confidants that are his own age. While he met a larger group of kids at Alexandria, we now know that they're pretty much all dead, a pattern which is the fate of many young kids on the show. With three different archetypal father figures to pull from the past, Carl will have many decisions to make regarding his future, his leadership skills and, with Enid, his shot at bringing in new life to a dying planet. Negan spared Carl's life by not bashing in his brains with Lucille but he did so by killing the innocent child inside the younger Grimes.