He is also very lonely. Plato doesn't have any friends before Jim moves to his town. He is also looking for a father figure. This is shown when he plays house at the mansion with Jim and Judy. They play house because none of them have stable families and that symbolizes how they lack family love.
Plato did not learn from his experiences or change because he got shot at the end of the movie.
Jim because he changed a lot and learns from his mistakes.