Even though their rivalry only lasted one episode, they argued so much and attacked each other so much. Seriously, if you watch the episode "Forging Forest Friendships" you'll see just how intense the rivalry between Froakie and Hawlucha is.

I just think the one with Froakie and Hawlucha isn't such a big rivarly.

^ Did you watch "Forging Forest Friendships"? They argued so much and even attacked each other.

At least their rivalry ended at the end of "Forging Forest Friendships". I doubt Piginte and Oshawott's rivalry has ended. The rivalry between Froakie and Hawlucha began because Hawlucha didn't like Froakie getting in his way during the Double Battle against Chespin and Bunnelby. The rivalry between Oshawott and Pignite began back when Pignite was still a Tepig because Oshawott kept stealing Tepig's food from him.