I have a few, but I'm convinced this guy is at the top of the chart:
He isn't hated by the community because of memes, he's just absolutely no fun to play against.
His kit's best use is a split pusher and he does that way too well. He can shroom up the surrounding area and then Sprint away at the first sign of danger. Very difficult to punish for being out of position and does not contribute much (healthy) gameplay to his team otherwise.
His Blind dart is a click blind that is hard to see during a team fight and does really good damage to boot. Quinn has to land a skillshot (or be in melee range) in comparison. Basically shuts down the ADC for a good portion of the fight and they got to do nothing about it. That's basically all he can do. When split pushing, it makes it so you need either a mage or a auto attacker and someone else in order to kill him since otherwise, he will just blind dart the auto attacker and kill them (which can sometimes also happen to the lone mage if they miss skillshots.)
His shrooms have a very negative impact on the "vision war." You are either required to get red trinkets to destroy his shrooms, while their team suffers no such penalty and have a major advantage, or just run into these high damage-revealing-slowing shrooms by chance and they still have an advantage. If a champion has vision tools on their kit, it should give them an edge in the vision war, not win it by a wide margin.