Corsola. Even with it's amazing ability (Regenerator) it's just pure useless with not enough power to be a damage output, not enough bulkiness to be a tank, not enough anything to be of use. Maybe a suicide lead with a sash, but even for that it is one of the worst possible options.
And honestly this should be explicitly about final evolutions. All first evolutions are useless, so it's kind of dumb singling out Magikarp, Caterpie, Weedle etc.