Kingdra is a massive pain to obtain, though. You need someone to trade with and then you need to go get a Horsea which you can only get near the end of the game in a kind of specific place while fishing. You also need to get a Dragon Scale, which I forget how to get in OR/AS so that might not be super hard.
On the other hand getting a Ludicolo in OR is pretty hard since I think it's a AS exclusive, so there's that.