Giovanni

Giovanni (サカキ, Sakaki) is the head of Team Rocket, and formerly served as the Gym Leader of Viridian City's Gym, known officially as the Viridian Gym. He handed out the Earth Badge to Trainers who defeated him. As a Gym Leader, he specialized in Ground-type Pokémon, but his master plan includes collecting rare Pokémon of all types. Upon arrival in Hora, it is revealed that Giovanni's, and by extension Team Rocket's, true goal is to revive Sacrelivo and descend the world into darkness.

Character
Giovanni reappears in Hora where he sets his true, evil plans in motion. Plans much more sinister than he had previously shown in Kanto and Johto. Like in previous incarnations, he is very mysterious, rarely directly involving himself in Team Rocket's dirty work, preferring to let his henchman do that much for him.

Pokémon
His choice of Pokémon has noticeably changed since his time as a Gym Leader, though they, at this point, remain unknown.

In the games
Giovanni is the primary antagonist of the games taking place in Kanto.

In the first games Giovanni appeared in, he served a dual role: one that was well-known to the residents of Kanto, and one that was more secret. He was first shown as the leader of the villainous Team Rocket, the first of many criminal organizations to grace the Pokémon games. After he and his team of Grunts were defeated at Silph Co. by a ten-year-old boy named Red, Giovanni fled to a hideout that his antagonist was unaware of. Once the player returned to Viridian City, one of the major plot twists of these games revealed that Giovanni, in addition to his role as a criminal, was the final Gym Leader to be fought before the Elite Four — albeit one without a formal title. He specialized in the Ground-type. Once defeated, he disbanded his Team and left the trainer with the Earth Badge and TM27 (Fissure). He then vanishes, and is not seen again.

In Johto, another group of Rockets tries to relaunch the old Team. They take over Goldenrod Radio Tower, and broadcast a radio announcement intended for him. Only in Johto is it revealed that Giovanni does hear the broadcast from his hideout in Tohjo Falls. An event involving a time-traveling Celebi allows Gold and Lyra to travel back in time and defeat Giovanni at the same time the rest of Team Rocket is being defeated. Like before, once defeated, Giovanni disappears.

Quotes

 * (To Team Rocket) "Team Rocket will rise again; greater, more powerful, and more feared than any other organization on the Earth. I have a plan, perhaps my greatest yet, to tilt the balance of the world into the favor of Team Rocket. We will begin soon. There is no time to waste. I will contact you again soon."