Quoted By:
So apparently there's this theory saying that jerk rivals never died, it's just that in X/Y you're the jerk rival. Your friends are super nice to you. Trevor wants to complete the Pokedex, the game is rigged in your favor, you will have seen more Pokémon than him, even if you're doing the minimum number of battles as possible. Serena wants to use mega evolution which is why she goes on her journey. There's only one mega stone to go around so she finds it, you battle her and take it from her, and then you grind her to dust for the rest of the game because you have mega evolution and she doesn't, when it's what she wanted. She gets her own mega stone in the post-game. That's when she gets to stand up to you.