>>47555231I agree that Silver has the most interesting character development of any rival, but I don't think he's the only character who grows over the course of the story.
Cheren learns that it's better to use the strength that you have to try to make a difference than to try to be the strongest of all.
Bianca learns that not everyone can succeed at what they set out to do, but they can still find a role they can succeed in.
Hop is kind of a discount combination of these two lol
NPC Calem/Serena learns that you don't have to go out of your way to set yourself apart from others and you can only do the best that you can do.