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Red>N>Cynthia.
Red's the only one who's ever been controlled by a player character which means he's "special" even by strong trainer standards, and he was one of the first who ever completed the Pokedex(in his region). He's also had the highest leveled team one can face outside of Battle buildings and was the final boss of GSC, far above his Blue who was a Champion himself and Lance.
N prior to his Champion battle simply switches teams with mons he's befriended shortly in the area before the PC battles them and has already gotten them to "supposedly" match the PC in strength in a relative short time. After his Champion battle where's beaten Alder, he's the only one of the three with access to a Box Legendary as well as the most variance in possible mons and teams he can and will use what with his Seasonal teams.
Cynthia is a Champion, something the prior two are as well as a bit of a mentor previous Champions didn't really show to the PC. She's got a pretty well-rounded team and two infamous fights in her Champion battle and BW, but her Garchomp is honestly what carries her reputation far more than anything else on her team does.
