There are some interesting similarities between these two characters. Both men are capable of great love. Atticus loves his children deeply and feels compassion for their struggles in growing up. Although George sometimes grows irritated with Lennie and speaks harshly to him, George loves Lennie, who is really George's only family. George looks out for Lennie much as Atticus tries to protect Jem and Scout.
Atticus and George are both men who will accept responsibility and do what they believe is right, regardless of consequences. Both are men of integrity. Atticus defends Tom Robinson vigorously, although his actions expose him to contempt and even danger, because defending Tom is his responsibility, both as a lawyer and as a human being. George accepts the responsibility of ending Lennie's life because shooting Lennie is the only way to save him from a terrifying and excruciatingly painful death at Curley's hands. George risks commiting a crime, and some would argue a sin, because he believes he is doing the right thing.
In To Kill A Mockingbird, Atticus says, "You don't understand a person until you walk around in his skin," and true courage is "when you know you're licked before you begin but you see it through no matter what." These words of wisdom from Atticus not only apply to his life, but also to George's life as well.
Atticus "walks around in many people's skin" which affords him the knowledge to teach his children tolerance with the people of Maycomb County. Likewise, George understands the men of the ranch and, thus, is able to use his perception to protect Lennie.
Atticus shows true courage by taking on the Tom Robinson case. Atticus knows that he will not win this case, but he takes it on anyway because it is the right thing to do. Similiarly, George knows that it will be tough to take care of and protect Lennie, but he promises Lennie's Aunt Clara that he will look after Lennie even though he knows Lennie will never be accepted in society.
Atticus also shows courage several times in the novel by standing up to the mob of townspeople in front of the jail, killing the rabid dog, and standing against a white family to defend a negro, Tom Robinson. George, too, shows this kind of courage by defending Lennie to the other guys, arranging Lennie's escape after killing Curly's wife, and finally, making the most difficult decision of his life, killing his best friend.