Giovanni

Giovanni is a major antagonist in the Pokémon franchise.

Games
In Red, Blue, Green, and their remakes, Giovanni is the leader of Team Rocket. His goal is to take over the world using Pokémon. He is encountered and defeated by Red on a number of occasions. After defeating Blaine, it is revealed that Giovanni was Viridian City's Gym Leader, and holds the final badge needed to access the Pokémon League. Once he is defeated, he hands over the badge, a TM (containing Fissure in Generation I and Earthquake in Generation III), and disbands Team Rocket.

In HeartGold and SoulSilver, a Celebi download allows the player to battle Giovanni (where it is revealed that Silver, the player's rival, is his son)

Anime
Giovanni appears much less in the Anime. He is depicted as a stereotypical villain and, like the games, uses his position as Gym Leader as cover for his crimes. He used to use Mewtwo as an "ultimate weapon" against challenging trainers, until the mutant rebelled against him. In Mewtwo Returns, he has a more major role, trying to recapture Mewtwo. He is thwarted and has his memories erased.