Tahm Kench
I'm sure this'll get lost in the huge, huge war between the LoLReddit fandom and the Boards fandom, both of which saying completely opposite things and calling the others 'bad' for not really understanding agreeing with the other side. I don't really care, I may as well try :)
Tahm Kench is a problem. He is a problem solely because he is toxic to fight. Yeah, sure, he's "balanced" in the statistical use of the word... but he's only balanced for two reasons: his inability to take towers effectively, and how common ranged bullshit is Top. Since most of that B.S is what people have a tendency to play, you can imagine the end result: Tahm being balanced relative to that broken B.S, but absolutely unfun to fight for anything that's not.
You have this topped with his 'frustration' factor, which is extreme. He will commonly take control away from the players' character, with no recourse. He will slow you basically forever. He will CC you for an upwards of 10 seconds at a time. He will damage you for 10-50% of your health. He will run you down no matter how much CC you waste on him, and due to his massive health bar you don't even want to waste the time killing him (esp. if he's fed.) This ties in with his 55% winrate before 25 minutes -- he's almost meant to tilt you and make you ff early, including with his menacing 5/0/3 KDA and infinite CC.
Tahm Kench, in his current state, is badly designed. Not in lore, not in thematics, but in terms of being something you play or play against, he is badly designed. You do not play as or against Tahm Kench, it's that simple. The player playing him goes through a static routine of three things in one order until Tahm gets a kill or falls off, and the people playing against him can't do anything about him until he falls off. End of story.
Tahm Kench isn't unkillable (because apparently "you can kill him, can't you?" is a reason that he's balanced, Jesus Fucking Christ) but, uh... next to Aatrox, Yasuo and all that jazz he is one of the most irritating, frustrating, unfun and uninteractive champions that you can combat. That can't be denied, especially if you look at how many people have issues with him.
