Why does george kill Lennie in the end of mice amd men?

Answer 1

George cares for and has a unique relationship with Lennie, so when Curly's lynching mob is coming to kill Lennie, he mercifully gives Lennie a quick, and painless death, by being shot in the back of the head with the same gun that was used in the execution of candy's old dog. the execution of the old sheepdog was foreshadowing the execution of Lennie. When the mob got there only Slim realized what had truly happened while the rest were stunned slim walked away with George and tried to relive him of his pain and guilt from killing his best friend.

Answer 2

George kills Lennie to spare him from a crueler fate at the hands of others. Lennie accidentally kills Curley's wife, and George knows that Lennie's intellectual limitations make it impossible for him to survive on his own in a society that might seek vengeful justice. George takes it upon himself to mercifully end Lennie's life to protect him from further harm.