One irony about the conflicting relationship of George and Lenny is the fact that George knows that he would be better off without the burden of caring for the mentally diminished Lenny:
If I was alone, I could live so easy. I could get a job an'work, an' no trouble...and when the end of the month comes, I could take my 50 bucks and go into town and get whatever I want.
However, he also understands Steinbeck's theme of the community of man that helps men measure the world. When asked why he travels with Lenny, George tells Slim,
I aint got no people. I seen the guys that go around on ranches alone. They ain't no good. They don't have no fun. After a long time they get mean...wantin' to fight.....'Course Lennie's...a nuisance most of the time, but you get used to going around with a guy an' you can't get rid of him.
In addition, the childlike Lenny--albeit the cause of their troubles--is the reason that George can keep alive the dream of having a ranch and happiness, a dream that protects them from a pedatory world. Once Lenny dies, George knows that the dream, too, is dead. Using an old cliche, George "can't live with him, but he can't live without him," either.
The characters of George Milton and Lennie Small are about as different as night and day. Steinbeck goes to great length to create very different personas for the two men, even making the two different physically. George is described as being small and quick, while Lennie Small is, ironically, a giant of a man. George is also quick-thinking and crafty; Lennie is mentally challenged.
Considering all this, conflict between the two characters is inevitable. George has promised Lennie's Aunt Clara that he will look out for Lennie, and he makes a sincere effort to do so. The combination of Lennie's enormous strength and his diminished intellect, however, leads to much trouble. George is continually rescuing Lennie from the consequences of his actions until at last, Lennie does something so egregious that George knows he cannot protect his friend any longer. When Lennie accidentally kills Curley's wife, the conflict reaches a climax which must be resolved. To spare Lennie from the mob, George kills his friend.