George is an interesting character, and there are a few dominant character traits that he possesses.
First, George is a quick-tempered man. This often comes out when he yells at Lennie for something. Even though he is quick-tempered, he is also very faithful. George stays with Lennie through all hardships. It would have been easier for him to go alone, but he always tries to take care of Lennie. Hence, faithfulness is probably his strongest trait.
Second, George is clever. He knows how the world works, and he tries to navigate himself and Lennie through a hard world. So, for instance, he has a contingency plan if something goes wrong. He tells Lennie to go to a designated area, so that they can escape together. From this perspective, George knows that the world is far from a perfect place.
Third, George is also an idealist. Underneath his tough exterior, George has a good heart, and he he dreams of better things. Most importantly he dreams of a farm that he and Lennie will have together. He desires to live off of the fat of the land.
“S’pose they was a carnival or a circus come to town, or a ball game, or any damn thing.” Old Candy nodded in appreciation of the idea. “We’d just go to her,” George said. “We wouldn’t ask nobody if we could. Jus’ say, ‘We’ll go to her,’ an’ we would. Jus’ milk the cow and sling some grain to the chickens an’ go to her.”
Finally, as for growth, George is one of the few characters, if not the only one, who actually grows. At one point in the story George confesses that he did not treat Lennie well. He learned it was wrong and he no longer does. Moreover, at the end of the novel, George has to make a very hard choice. He decides to take Lennie's life as an act of mercy. He knows that Curly's men will kill Lennie in a horrible way. So he he puts Lennie down. In this sense, George also grows, as he realizes that he can't help Lennie any further.