Lennie is a sympathetic character because he isn’t smart and can’t remember things. We know this because on page Lennie couldn’t remember what to do when the boss talked to them a fact that Lennie told him only couple of minutes ago. We also know because George says “I ain’t sayings he’s bright. He ain’t.” on page 22. Lennie being not so smart gets into trouble when he want’s to feel the girls dress and dosen’t know that that’s not ok.
Another trait is that is nice and always means well. For example