I agree with most folks on saying hate is being a bit overkill. However, I have two major dislikes to mention.
Jynx, without a doubt, tops my list. That thing will NEVER have the honor of gracing my team due to all the contraversy surrounding it. Yes, it includes skin tone; and being African-American it still rubs me the wrong way...at least they remade it purple; but to be honest its really beating a dead horse to resurrect that topic, isn't it?
Besides her, Klink's family takes the closest thing to what I personally consider blatantly poor design, and maximizes it. Sure we've had Eggs, sludge, and wind chimes, but at least Vanillite (another borderline dislike) had the distinction of being adorable.
To me, Klink's family has almost sub-zero redeeming qualities. What you see is exactly what you get from that thing; which I feel contradicts part, underscore PART, of what this franchise is all about: there being more than what meets the eye of otherwise cuddly partners. And unlike Exeggcute, it doesn't even have unique typing to make it more than what it's based on! Haha.
...A wise one once told me love was like a pokemon battle. You can fight it, you can run away from it; or you can end up without any balls when the opportunity arises.