Agatha

Agatha is a member of the Elite Four in Generation I and its remakes, who uses -type Pokémon. She was Professor Oak's rival when they were young. She also makes an appearance in the anime, where she battles Ash while she is the temporary Gym Leader until someone could be found..

In the anime
Agatha appeared in The Scheme Team. She was acting as the temporary Gym Leader of the Viridian City Gym when Ash came through on his way to Pallet Town. Ash ran into Scott and met Agatha, to prove his strength to them, Ash challenged Agatha but lost to one of her Pokémon, Gengar. After losing, she revealed she is a member of the Kanto Elite Four. But, impressed by his strength, both Agatha and Scott suggests Ash take on the Battle Frontier.

FireRed and LeafGreen
Rematch

Pokémon Stadium
Gym Leader Castle

Gym Leader Castle Round 2

Trivia

 * Apparently, in the Game and Manga, she mentions Professor Oak, this could mean that she used to have some kind of relationship with Professor Oak.
 * In her Generation I sprite and artwork Agatha had long gray hair.
 * All of her Pokémon in Pokémon Red/Blue/Yellow are part -type.
 * In her first battle in FireRed and LeafGreen, all her Pokémon are female. In the second and subsequent battles, they are all male.
 * She is considered by many to be the creepiest Elite Four member.
 * Agatha seems to bear a little resemblance to Bertha.