I believe George and Lennie were true friends still, even though George shot Lennie. They were very close and I don’t think George wanted to shoot Lennie, but he didn’t have much of a choice. If Curley would have found Lennie before George did, most likely he would have hurt, tortured, or even killed Lennie, because in Chapter 5 of Of Mice and Men, Curley tells Carlson to shoot Lennie in the guts as soon as he sees him, tells Whit to go to Soledad and get the deputy sheriff, and tells George to join the search party for Lennie. So either way, if Lennie were found by Curly, it would have probably been a much worse way to die, rather than being shot by George.
I do not believe that what George did was necessarily a bad thing. I just think that he did it to protect Lennie so that he would not have to suffer, but instead George shot Lennie and got it over with quickly so that neither George nor Lennie would have to feel as much pain. Evidence from the book also states that although George really does love Lennie, Lennie has endangered and scared many of the people around him. In one situation, when he accidentally ripped off the dress of a young woman