Pokemon Red and Blue is where the adventure started, with Venusaur being one of the most powerful creatures of Generation I.
Even to this day, Venusaur remains a force to be reckoned with. It has only gotten better, honestly. The final evolution of Kanto's Grass-type starter is incredible.
Venusaur was extremely underrated in the first Generation of Pokemon with the likes of Blastoise and Charizard available for selection. Regardless, those that chose Venusaur were not disappointed, with the right moveset.
The best moveset for Venusaur in Pokemon Red and Blue
Sleep Powder is a wonderful move to give Venusaur. It gives it ample time to put the hurt on opposing Pokemon. Its accuracy is a bit low, but when another Pokemon is put to sleep, Venusaur can do some serious damage. In the Generation I games, it can even put an opponent to sleep behind a Substitute.
Venusaur has a great Special stat and a pretty good Attack stat in Gen I. Using Swords Dance will increase its Attack stat by two stages. With opposing Pokemon put to sleep, being able to pull off a Swords Dance without worrying about an attack is invaluable. It can be taught by TM.
Razor Leaf is one of the best Grass-type moves in the first Generation of Pokemon games. It deals solid damage and has an increased chance of landing a critical hit. This is a move that can be learned by Bulbasaur or Ivysaur pretty early in the game, depending on how fast the player levels them.
Body Slam will give Venusaur some coverage against Pokemon that have a resistance to Grass-type moves. Venusaur can learn this via TM. Body Slam cannot paralyze Normal-type Pokemon in Red or Blue, but has a 30% chance to do so to any other type that can be hit by the move.