The only thing wrong with Bellsprout is that he/she looks so silly.
Victreebel is really one of the most kickass Pokemon ever
The real issue is suckish Grass/Poison typing
Ice, Fire and Psychic are really common for attacking
If you can support it okay (This may mean Wish users) it can rip stuff up
If you are a wizard and have Castform it can actually learn Weather Ball
Using this + Growth, Sludge Bomb, and Leaf Blade is pretty deadly on it's own
BUT
If you toss in a Sunny Day user and switch into something it can handle, i.e Tyranitar, it will forget stuff up
