Buck longs for his life of ease in California before he was stolen from his home in Jack London's Call of the Wild. As the top dog on Judge Miller's ranch in the Santa Clara Valley, he lives a life of freedom and independence. When the ranch hand, Manuel, steals Buck to pay off a gambling debt, Buck learns about another side of human violence. His mistreatment by his owners, his constant hunger pangs, and the brutal punishments inflicted by the club turn Buck into a different kind of animal. His dealings with the lead dog, Spitz, show him that other animals can also display extreme cruelty. Buck remains an angry dog until he meets up with John Thornton, whose displays of love lead to the happiest days of Buck's life as a sled dog.
Lots of people and animals do things to Buck or to people he loves that make him angry. Let me list a few of them.
First, the man in the red sweater beats Buck to make him be obedient. Buck, of course, gets angry about that but cannot do anything about it.
Second, he gets mad at Spitz for laughing when Curly is killed. He continues to hate Spitz when Spitz is the lead dog. Finally, Buck kills him.
Last, he gets mad at the Indians after they kill John Thornton and the other gold prospectors. That makes him really angry because he loved Thornton.
There are other times when he gets mad as well, but these are three major ones.