I wish an older rival for Ash, which points out the flaws the boy has and deconstructs his worldview in very precise details, which in turn breaks him mentally as a result. To add salt to Ash's wounds the rival beats his entire team using a pokemon he just caught. And the icing on the cake would be, that he is revealed as a good guy all the time along.
Yes, I love to see Ash suffering. It might be cruel, but how are you going to change the unchangeable 10 year old child?