When his parents aren't physically and or verbally abusing him, they're ignoring him. Johnny can stay away from home for long periods of time and nobody seems to care or notice, in sharp contrast to Pony's situation.
To make things even worse, Johnny was brutally beaten by the Socs last spring and now lives in a constant state of fear and PTSD:
I had never been jumped, but I had seen Johnny after the four Socs got hold of him, and it wasn't pretty. Johnny was scared of his own shadow after that. He was sixteen then. (1.7)
On top of that, he doesn't quite get enough to eat, he often sleeps outdoors, and is even contemplating suicide. The gang makes up Johnny's entire support system, but since they're struggling kids themselves, this support is far from sufficient.
Even though Johnny has had crummy role models, he's tries to stand up and be a good person. We never see him being mean or mistreating others. He even challenges his idol, Dallas, when he sees how uncomfortable Dallas is making Cherry and Marcia at the movies. Of course, this connection with the girls has some disastrous consequences since their boyfriends are Randy and Bob—the very Socials that beat Johnny so badly earlier in the year.
And that gets us into one of the trickiest territories of the novel—Johnny's killing of Bob. Since the story is told from Pony's point of view, we never get the full details of the killing. All we know is that when Johnny stabbed Bob, David stopped trying to drown Pony in the fountain. Johnny saved Pony's life. But how do you feel about this? Did Johnny do the right thing? Did he have other options? Did he act in self-defense?