10 Worst Middle-Stage Pokémon

These two Pokémon share the number 5 slot because they're essentially pallette-swapped versions of the same Pokémon.

Silcoon and Cascoon both evolve from Wurmple. Normally, a cocoon Pokémon isn't so bad in that it ascertains a quick evolution into the desired final form. While the "quick evolution" part still applies (it will evolve into Beautifly or Dustox at level 10), the issue is with how it evolves.

See, instead of Wurmple having a gender-specific evolution line or an evolution line that depends on happiness, time-of-day, or anything like that, Wurmple evolves depending on its personality value. Not only does the player have no say in what a Pokémon's personality value is, but they also have no way of seeing what their Pokémon's personality value is.

As such, evolving Wurmple into a Silcoon or a Cascoon is literally trial and error.

Theoretically speaking, a trainer could evolve 15 Wurmples and not have a single one of them evolve into a Cascoon, or vice versa. Evolution is supposed to be an accomplishment, not a game of chance. And for such mediocre Bug-types as Beautifly and Dustox as the end result, it makes toiling for these two worth nothing more than a Pokédex entry.