Hmmm... this is interesting... so many pokemon I like have been bashed xD
Normal: Dunsparce - It's useless and has a terrible design, need I say more?
Fighting: Hariyama - Not only is it outclassed by better pokemon but I HATE IT'S DESIGN SO MUCH.
Flying: Skiploom - It's not that good and it looks ridiculous.
Poison: Gulpin/Swalot/Trubbish/Garbodor - All tied for bad design and for sucking.
Ground: Stunfisk - It's got great typing but it's stats and moves are a let down and quite frankly it design could have been a little better.
Rock: Nosepass/Probopass - Stat and move wise they are okay... but... they have pointless giant noses as their main feature... lolwhat?
Bug: Probably Paras/Parasect - I don't HATE them but they have terrible typing and really they don't have stats good enough to back it up and also... WHOSE IDEA WAS DRY SKIN ON A BUG/GRASS.
Ghost: Dusclops - Ugliest ghost type in existence and it is painfully slow... at least Duskull and Dusknoir look good.
Steel: I like them all really but my least favourite would be Beldum - It's weak, ugly and boring with its only redeeming quality being that it evolves into metang and metagross.
Fire: Slugma - It's weak and ugly, not good traits in a pokemon.
Grass: Sunkern - Worst pokemon in the game, that is all.
Water: Luvdics - Nearly as weak as sunkern, about as usefull and without the almost redeeming quality of evolving... although it is slightly better I guess.
Electric: Chinchou - I don't hate it really but I figured I had to pick one and it has a dorky design.
Psychic: Unown - The concept, movie/anime versions and design are pretty good but in game it is the most pointless pokemon around. I almost want to take back saying sunkern is the worst but inown has better stats.
Ice: Jynx - Just because it is so ugly.
Dragon: Dragonite - The pokemon itself is awesome but I hate how we go from an elegant pokemon like Dragonair to something with a design the polar opposite.
Dark: Vullaby - A pokemon with terrible stats that evolves late should at least look good, Vullaby does not.