Is Slim a lonely character? How?It seems like Slim and George have each other to talk to. They get along pretty well. Does that mean that, after...

Slim is a lonely character in the sense that not many in
his world match his level of skill, intelligence, and sensitivity. He is described in
narration as godlike in comportment; when he speaks, men listen. Even Lennie, whose
memory is terrible, remembers Slim. When George questions Lennie about Slim and Curley's
wife possibly being in the barn, Lennie is able to tell George that Slim had been alone,
and had told Lennie not to pet the pups so much.

Perhaps
the only character in the novel for whom Slim felt  companionship was, indeed, George,
but as the answer above states, George seems primed to go about the rest of his life in
the way he described to Lennie in part one: in cathouses, drinking whiskey and shooting
pool.