>>41782387he goes from being an idealist and energetic trainer that thinks he'll be the one to unseat his brother and become a legend. he gets slightly unnerved but still confident even though he can't beat (you), thinking it's only a matter of time and that (you) are just an amazing rival. then he loses extremely badly to bede, and he has to realize that maybe he's not the legend he sees himself as. He grows to realize that (you) are the one that might do everything he dreamed of, and is quite bitter about this. You can see it progress in the way he reacts to each defeat by your hands every time you battle him. even after you become the champion, he still harbors some dreams of finally blooming and coming into his own and then gets trashed by one of the squidward brothers. he realizes during the post game that his dream of chasing after his brother's coattails wasn't what he truly wanted to do, and matures a little bit by realizing that he just likes to help people.
the most interesting thing about Hop is that unlike shithead rivals like Silver and Bede or friendly rivals like Wally, he actually goes through what it's like to be an NPC when he is literally an NPC.