Greninja, I just don't like its design, don't see the appeal and how popular it is cause it's a ninja frog who's really good in competitive play and the amount of attention it got to the point where the anime made up a completely new nonsense form for it, practically giving it a Mega, is ridiculous.

TBH I don't really hate any Gen 6 pokemon, I'm fine with most of them. When I first saw Froakie when it was revealed in 2013, didn't expect it to become Charizard/Pikachu tier in popularity.

My least favourite Gen 6 Pokemon is Binacle. I normally don't dislike Pokemon for design alone, but Binacle's design is so awkward, I can't even tell what it's supposed to be.

I also don't like Furfrou. I think it's ugly. And yes, I know you can trim it to make it look better, but I find it unfair that the trimming mechanic is restricted to this thing alone. Also, I think Furfrou is annoying.

probably Dedenne, pikaclones were never really my thing

I think Gen 6 has some incredibly good designs (Chesnaught <3, Aegislash, the ghost/grass duo, the birds) but I also think it has some of the most forgettable (bergmite and avalugg) as well as my least favorite line: Swirlix and Slurpuff.