Joffrey Baratheon brings all fans of the novels and television show together, united under one voice. While some readers might like Catelyn and others be frustrated by her, some viewers might pity Bran and others find him annoying, everyone—and we mean everyone—straight up hates Joffrey. But does the child King of the Seven Kingdoms really deserve such scorn? The short answer is absolutely. The long answer is a less resound absolutely because of some complicating factors.
Joffrey is simply and utterly cruel. He lacks any sense of empathy and is essentially what would happen if you made Ted Bundy king and said, "Go Nuts!" There are so many choice examples of Joffrey's cruelty that we don't even know which ones to pick. So here's a smorgasbord of evidence:
And with that, we can't stomach listing any more. Seriously, this kid is just the worst.
But let's complicate the issue by bringing up the king's parents.
Joffrey believes he owns the people of his kingdom, as though they are his playthings—we see this in small moments throughout the novel, like when he calls Sansa like a dog or treats her like a doll (58.Sansa.6-7). We're willing to bet he learned a lot of this mentality from his mother, who is notoriously not a fan of the "smallfolk."
During the Battle of the Blackwater, citizens gather to find safe haven in the Red Keep. Cersei commands the Kingsguard to send them home and notes, "If they won't go, have our crossbowmen kill a few'" (61.Sansa.28). Sounds familiar, doesn't it? It would fit in nicely with the smorgasbord of awful we listed above.
Additionally, Joffrey is always miming his mother's words—"Fear is better than love, Mother says" is a nice example (33.Sansa.49). Speaking of miming, Robert's love for all things war and killing likely rubbed off on his son.
Let's also not forget that Joffrey is still a young man—a boy really—so when he injures himself on the Iron Throne, he cries out for his mother (66.Sansa.45). Evidently, he still relies heavily on her for emotional support and likely moral guidance.
Now we're not going to say Robert and Cersei are entirely to blame for Joffrey's, um, Joffrey-ness. But we will say that they certainly didn't seem to help matters, and this complicates the picture of Joffrey many readers have.
Importantly, Joffrey's younger brother and sister, Tommen and Myrcella, are nowhere near as fiendish as him, which kind of diminishes how much we can hold his parents responsible for his terribleness. Tyrion thinks Myrcella confronts leaving home for Dorne with "courage and dignity" (42.Tyrion.2), two words we're pretty sure have never been associated with Joffrey. When Prince Tommen cries, it is Myrcella who comforts him—Sansa even thinks that she wouldn't mind marrying Tommen and wishes he were the eldest Baratheon (3.Sansa.87).
Since they had the same parents, how did these two people end up so completely different than Joffrey? We suppose it was one part nurture, and two parts nature. Or something like that anyway.