Venusaur

Type Tier
Grass / Poison BL
Statistics
Stat
HP
80
363
Atk
82
262
Def
83
264
SpA
100
298
SpD
100
298
Spe
80
258
Name Item

Stalling Venusaur

Leftovers
Moveset
~ Synthesis
~ Leech Seed
~ Razor Leaf
~ Reflect / Sleep Powder

The stalling Venusaur. Put something to Sleep and stall it out with Leech Seed and Razor Leaf. Or Reflect + Leech Seed works too. You probably want Sleep Powder; Meganium outclasses it in stalling in every way.

Name Item

Swords Dancing Venusaur

Leftovers
Moveset
~ Swords Dance
~ Body Slam
~ Giga Drain
~ Sleep Powder

This is a good idea in theory, but loses to Skarmory, as do many "good ideas" involving physical sweepers. Swords Dance, then put any possible counters to sleep. Hopefully Body Slam will grant you some paralysis for fast counters, and Giga Drain will waste Rock, Ground, and some Water-types (in addition to replenishing some health). Sadly, Venusaur cannot learn Sludge Bomb in GSC, so something like Victreebel will be able to hit a lot harder. If you want to, you can slip Synthesis over Sleep Powder for more recovery (in which case you could use Razor Leaf instead of Giga Drain) because Venusaur has awesome survivability.

Other Options

Venusaur does learn Light Screen, which is a somewhat rare move. You could also use a Growth set.

Opinion

Great overall stats, but inferior to Meganium due to the typing. Venusaur doesn't learn Sludge Bomb in GSC; if it did, it'd probably be a lot more popular. In addition, the move Razor Leaf first also lost the incredible Critical Hit rate that it had in RBY, making it less of a threat.

Counters

Fire, Flying, Poison, and Steel Pokemon are all resistant to Grass and hit Venusaur pretty hard. Special mention goes to Skarmory for its quadruple resistance to Grass and resistance to Body Slam, and its ability to Whirlwind Venusaur out if need be. Celebi and Exeggutor are immune to Leech Seed and strike back with Psychic.