Grass- Amoonguss. Spore is really irritating, and Amoonguss is a Pokemon that can take a hit and use Spore. Worst of my nightmares.
Water- Tentacool. Surf for 5 minutes, and you'll understand this.
Fire- Magcargo. I've found it useless, and the 4x weakness to a common type severs it even more.
Bug- Spinarak/Ariados. SPIDERS. ;_;. The Joltik line get the miss from this, due to the Electric type being one of my favourites.
Normal- Tie between Bibarel and Dunsparce. I've said this in the top 10 least favourite Pokemon thread, and I'll say it again: DERPY.
Dark- Shiftry. Awkward as hell stats, and an even more awkward ability set. It also looks like a ninja Pinocchio. Odd.
Psychic- Hypno.
Hopefully it's not too obvious.
Ghost- Sableye. PRANKSTER NEEDS TO BURN.
Poison- Muk. Sluuuuudge.
Ground- Dugtrio. Why have 1, when you can have 3? Unlike Magneton, mind you, Dugtrio isn't good. At least, to me.
Rock- Ew, the Rock type doesn't have any Pokemon I really like, besides Terrakion and Archeops. This goes to Geodude. The Tentacool Effect.
Steel- Steelix. I blame Jasmine.
Electric- Pachirisu. Irritating, useless, a waste of space.
Ice- Abomasnow and Mega Abomasnow. Frost tree and tree in a giant snowball. Nuff said.
Dragon- I don't really dislike any dragons, so I'll just put one I don't approve of due to overratedness: Goomy. THE MEMES THE MEMES
Fairy- Klefki. Swag keys can disappear off the face of the earth (blame prankster)
Fighting- Hitmontop. Its stats are all underwhelming to me, and its appearance is weird to me...Beyblade Pokemon? No more crossovers please.
Flying- Combee. Ew ew ew ew another bug/flying type. This one's the weakest, too. Oh, poor 4th Generation...my favourite gen, yet the one that produces some underwhelming Pokemon.