The complete Pokemon RBY pokedex, part 8

Pokémon Name: Slowbro
Type: Water/Psychic
Classification: Hermit Crab Pokemon
Pokédex Number: 080
Ability: Oblivious and Own Tempo
Dream World ability: Regenerator
Useful Attacks: Psychic
Location Found:
D/P/P: Evolve Slowpoke
HG/SS: Slowpoke Well, Seafoam Islands, Tohjo Falls, Safari Zone (Rocky Beach, Peak)
B/W: Abundant Shrine (via Surf, bubble spots only)

Withdraw is the only new move you get when evolving into Slowbro, plus some moderately increased stats. Its speed stat is still hilariously low, though not quite the lowest in the entire game. Focus on moves in the special attack category, like Psychic and Water Pulse, and you should be fine.

Evolution: From Slowpoke