N is the former Unova Champion and former leader of Team Plasma whose ambition is to release all Pokemon from Human suffering. He goes into self impose exile after realizing the “Truth” from Black. He can listen to the inner voices of Pokemon allowing him to actually communicate with them. It’s unclear whether this gift is similar to Yellow/Lance from Kanto. He is a strong trainer who defeats Champion Alder and awakens the Legendary Pokemon Zekrom. In Black And White 2 Manga he appears before White ordering her to leave the White Ball. In the future we suspect that Zekrom would fuse with Kyurem leaving N helpless to stop Black Kyurem.
Diantha is the current Kalos league champion and one of the major factors in stopping the rampage of Team Flare. Her signature Pokemon is Gardevoir and she too can use Mega Evolution with Perfection. She is also an actor when not busy saving the Pokeworld or defending her title. In fact she is possibly the strongest trainer in Kalos when it comes to Mega Evolution. While in the list it was tough deciding between Cynthia and her, Diantha makes it to the List mostly because of Mega Evolution.