We could work backwards on this one. The ending of George killing Lennie shows the ultimate in care. The very idea that George does not want Lennie to be killed by the mob led by Curley and Carlson shows a care. He recognizes that Lennie is not going to escape. His comforting tone and demeanor towards Lennie in the last scene is reflective of his care. The last words that Lennie hears is the dream that he and George are to share. This is something that reflects care. Throughout the novel, George recognizes that he and Lennie need to be inseparable. In a world where there is so much fragmentation and isolation, George recognizes that he and Lennie need to be together. When speaking to Slim, George acknowledges that he made a promise to Lennie's Aunt Clara and this demands that he look out and take care of Lennie. At the same time, it is evident that George looks out for Lennie when he warns him of what to do and what not to do. George really does not gain much from his taking care and protection of Lennie, and it is in this mold in terms of how both of them "stick together" that reflects how much George actually does take care of Lennie.
From the beginning George exhibits solicitous, or caring, actions toward Lennie.
Soon after their arrival in the clearing, Lennie flings himself down at the sight of a pool covered with algae, gulping the water from his huge "paw." Immediately George scolds him, telling him not to drink so much while also expressing his doubts about the water's quality. Then, as they discuss the new job to which they are reporting the next day, George reminds Lennie that he holds both of their work cards. Further, he instructs Lennie to keep quiet; George will do all the talking when they meet the boss tomorrow. Both these actions are done to protect Lennie.
George acts much like an older brother to Lennie: He complains that he could get along better sometimes without Lennie, but he also speaks of their fraternity as he mentions how other "bindle stiffs" roam from job to job and are very lonely, unlike them. George and Lennie always have each other, as George states whenever Lennie asks him to recite their "dream" of owning a farm and having rabbits for Lennie to pet. The two men often speak of this dream of someday owning a little farm. This hope provides the two companions something for which to strive together, and George's speaking of this dream makes Lennie happy.
Despite their hopes for a place of their own and all George's cautionary words, Lennie gets himself into trouble much as he did in their previous workplace. This time when he is alone with a woman--the wife of the boss's son--she has him feel the softness of her hair, but Lennie pets her roughly and she becomes frightened. The more she struggles, the more Lennie tries to quiet her out of fear that he will get into trouble. Unfortunately, he shakes her and grips her so tightly that he breaks her neck and she dies.
Because of his fear that Lennie would again get into trouble, George has already instructed his companion to hide where they previously camped if anything serious goes wrong. When he finds Curley's wife dead, their dreams die, too. George and Lennie's tragedy of frustrated hopes comes to an end when George shoots Lennie in order to prevent the terrible consequences that would happen if Curley and the others were to catch him.