Unown aswell for the same reason, has hidden power which can be learnt by nearly any pokemon.
though with unown, they have an interesting theme to them, with the letters and everything, they do look pretty cool as a collection.
Other than this, i would have to say dunsparce. It has terrible stats, for a leveling up movepool, its moves are terrible. It doesn't evolve, it looks.. weird, and to be honest i think everyone forgets about this pokemon as it never is the worse stat wise, but it has nothing good about it to be remembered. Ontop of this, it is terrible for a normal type, and it seems incomplete, it is as if it was supposed to have an evolution but was just forgotten about.
So i would say one of the worse is the forgotten Dunspace