I just love these kinds of topics. It reminds me of all the horrible Pokemon there are... ;-;
Generation I
Machop/choke/champ - Design Factor - I'm the worst when it comes to Fighting-type Pokemon; there are very few of them that I'll actually say I like... and the Macho-family are certainly not a part of that list. Maybe I'm just too harsh on the Pokemon, but I just really hate the over-confident expression they give them all. It makes me so glad that they brought out some actual cool Fighting-types, over the Generations...
Mr. Mime - Design Factor - This is probably the second creepiest Pokemon I've seen. Though the dislike is mostly on the design than much else, but when I watched the TV show, I know I certainly didn't like that Mr. Mime that became Mrs. Ketchum's personal slave stalker.
Generation II
Wobbuffet - Design/Existence/Use Factor - My absolute least favourite Pokemon is definitely Wobbuffet, along with it's pre-evolution, Wynaut. But more on that later. This is probably the ugliest Pokemon I've seen, and probably the worst, on top of that. I dislike how it is used, in particular with later Generations that gave it the annoying ability to trap a Pokemon in battle when it's on the field with Shadow Tag. Frankly, I view Wobbuffet as a wasted slot for a better Pokemon. Heck, even a cool Fire-type would have better filled that spot! ...and the female form... wears lipstick... *shudders*
Heracross - Use Factor - Not so much a least favourite Pokemon, but one that has been the bane of me in online play. I've been demolished by it so many times that its appearance has become one I despise.
Generation III
Mudkip - Meme Factor - I used to love Mudkip when I first got my hands on Ruby... but when I started seeing what the Internet had done to it, I soon started to dislike it. Especially when a specific website, as an April Fools' joke, decided to force everyone's avatars as a "So I herd you liek Mudkipz?" gif. I haven't liked Mudkip since, though at least Swampert is awesome.
Wynaut - Design/Existence Factor - The same issues I had with Wobbuffet, though something I've never seen used in battle. Wobbuffet was probably the worst Pokemon to consider even giving a pre-evolution to... much like Wobbuffet, it was a slot in the Third Generation that could have been filled in with a much better Pokemon.
Generation IV
Bidoof/Bibarel - Design/Existence Factor - While I note it as a design factor as well as, it's primarily the existence of this Pokemon that eludes me... I know it fills the slot of obligatory Normal-type found in the first few Routes... but were the design team FAST asleep when they designed this? Yeah, a beaver Pokemon is a nice idea, but I'd have liked a better-looking beaver than the... 'unaware'-looking one we were given. This thing would give even Slowpoke a run for its money on how spaced-out it looks. It doesn't look cool in the TV show, either; it looks stupid.
Kricketot/Kricketune - Cry/Design Factor - Oh. My. GOD, are Kricketot and Kricketune annoying. Whenever I'm in areas where these Pokemon exist, I have to mute the volume so that my head doesn't explode from chronic migraines... perhaps not Kricketot as much, but certainly its evolution. Its one heck of an ugly Pokemon, and I'm happier knowing that they aren't hounding me in Unova...
Mime Jr. - Design Factor - If Mr. Mime is on my list, it's only natural for Mime Jr. to be there, too. What I'm glad about is that, with Generation V, we've moved away from silly pre-evolutions that aren't really needed. Though... I guess I can understand the existence of Mime Jr.... somewhat. I would have much preferred a Tauros/Miltank pre-evolution, though. Or an additional Eevee evolution. ...anyway, what I'm trying to say is, I'm not fond at all with the design of it.
Generation V
Pignite/Emboar - Design/Typing Factor - I loved the design of Tepig! I thought it would have some really cool evolutions that finally strayed away from the Fire/Fighting-types that had followed on from Generation III's Blaziken... but much to my dismay, we were given... this... yeah... I honestly feel sorry for every Tepig that has advanced through evolution... ;-;
Patrat/Watchog - Design Factor - I think this is as bad as Bidoof/Bibarel. We haven't really had a decent Normal-type early Routes Pokemon since Generation II. Frankly, I just really don't like its design.
The Grass/Fire/Water-type Monkies - Design Factor - I appreciate what they did with these Pokemon, but couldn't they have chosen something that wasn't monkey-related? What makes it worse is they're essentially carbon copies of each other, just with a different type attached... and what the heck is wrong with Simisear!?
Scraggy/Scrafty - Design Factor - Scraggy and its evolution fall into the design trap that the Macho-family did, only in a different way. Some people say that its a cute Pokemon, while I frankly find it rather creepy... admittedly, it is kinda cute what it's sprite animation does... but it still has that face... *shudders* Well. I guess at least it isn't Wobbuffet...
Klang/Klinklang - Design Factor - I'm somewhat okay with Klang, but Klinklang is what really bugs me... at least Magnezone had a different look about it; this is pretty much just Klang with the spinning disk thing from Balamb Garden in Final Fantasy VIII floating around underneath it! It has to be another case of "Were they sleeping when they designed this?"-- it just has to be...
Tornadus/Thundurus/Landorus - Design Factor - This has got to be the laziest designing I've seen. Even lazier than Klinklang, for the almost literal fact that these are just recoloured sprites of each other! I honestly couldn't believe my eyes when I saw these three Pokemon, and though they have their small differences, they're still essentially the same Pokemon, with different types and a new lick of paint.
I think I've waffled on long enough about my dislikes in the terms of Pokemon. I've probably missed some in there somewhere, but I'm far too tired to really care, at the moment... xD;;