Here's why:
* Denial: Dally refuses to accept Johnny is truly gone. He clings to the belief Johnny is still alive, even when presented with concrete evidence to the contrary. He reacts with anger and violence when confronted with the reality.
* Fantasies: Dally imagines scenarios where Johnny is alive, even going so far as to steal a car and drive to the hospital, believing Johnny will be there. This fantasy is fueled by his desperate need to believe Johnny is not gone.
* Self-destructive Behavior: Dally's grief and denial manifest in reckless and self-destructive behavior. He engages in criminal acts, knowing they will ultimately lead to his own death, perhaps hoping to join Johnny in death.
While other characters also grieve Johnny's death, their reactions are more grounded in reality. Dally's reaction is the most extreme, demonstrating a clear disconnect from the facts and an inability to cope with the loss in a healthy way.