Bellossom

Type Tier
Grass UU
Statistics
Stat
HP
75
353
Atk
80
258
Def
85
268
SpA
90
278
SpD
100
298
Spe
50
198
Name Item

Double Powder

Leftovers
Moveset
~ Sleep Powder
~ Stun Spore
~ Moonlight
~ Razor Leaf

Double Power (Sleep Powder and Stun Spore on the same moveset) is always fun to try. Synthesis gives constant recovery, and Razor Leaf is a good STAB attack. Good for switching in on Rhydon or Marowak.

Name Item

Swords Dancer

Leftovers
Moveset
~ Swords Dance
~ Sludge Bomb
~ Hidden Power Ground / Razor Leaf
~ Sleep Powder

Physical attacking moveset. Victreebel and even Vileplume pull this off better thanks to STAB on Sludge Bomb and better speed in Victreebel's case, though. You could use Moonlight to keep you at full health to Swords Dance more.

Other Options

Giga Drain because of STAB. Reflect + Leech Seed could annoy Cursers and force them to Rest, allowing you to counter appropriately.

Opinion

Bellossom is a cool Pokémon. It has the pure Grass typing and can use both Stun Spore and Sleep Powder, unlike Meganium. In addition, it isn't weak to Rock Slide like Jumpluff and has good Special Defense unlike Tangela. Movepool is fairly limited, but that's a characteristic of most Grass Pokémon.

Counters

Arcanine can use Fire Blast to roast Bellossom, and often carries Sleep Talk, anyway. Zapdos has Drill Peck and Sleep Talk. Steels such as Skarmory easily counter Bellossom's attacks. Forretress, Scizor, and Skarmory in particular can use their STAB moves to hit Bellossom super effective. Grass / Poison-types like Victreebel and Venusaur can Sludge Bomb Bellossom for its doom. Heracross can easily take whatever Bellossom throws at it and fire off a Megahorn.