Who is Maxie in Emerald who wants battle you?

There is no character named Maxie who wants to battle you in Pokémon Emerald.

It's possible you're thinking of Archie, the leader of Team Aqua. Archie is a major antagonist in Emerald, and you battle him multiple times throughout the game.

Could you be thinking of a different game or a different character? If you tell me more about who you're thinking of, I can help you figure it out.