Before anything I'd just like to say, this is just my opinion and my guess as to how these battles would go down. I picked who'd vs who based on powers. And for the most part each character will only have one opponent. I kept all bias out.

Musa vs Asami
First of all I chose these two to vs because no one in avatar can music bend and and Asami because she needed an opponent.

For this one (as much as it kills me to say it, because I love Asami) Musa defiantly has the upper hand. Whilst Asami is an amazing fighter and has her crazy electro-glove fighting a bender and fighting a fairy are two different...

Mai walked inside the woods, and a portal appeared. "What the whatta?" she asked as she enters it. She then appears at the Omega Dimension. She saw three man (Wizards Of Black Circle) and stares at them. "They look evil - but maybe I can use them for Stella," says Mai evilly. The frozen wizards didn't move a bit. Mai then thought another time. She made her decision. She took out a tool from her pocket and breaks the ice.

"You have freed us, girl," thanked Anagan. "I freed you for a reason," says Mai. "We will fulfill your wishes," smiles Ogron. "There's a girl in Ba Sing Se, her name is Stella...