I would definitely choose Curley's wife and Crooks for analysing good and bad, because both people are quite misunderstood so there's a lot to say there. With regards to completely good or bad, Lennie is the most definite character in that he is all good, obviously due to his childish nature, which demonstrates the innocence that Steinbeck is trying to portray (I know this book inside and out having done my GCSE's hahaha) Good luck!