Like, what a champion is suppose to be, having no correlation to their character, their design, and/or their kit.
I think that honor goes to 
Karthus, the Deathsinger.
He is suppose to go around singing, and adding the spirits of anyone who he has written into his book into his ghostly choir. He doesn't do any of that. Like, outside of his passive, his entire kit could belong on any generic spell caster.
Kaisa is an abomination of design honestly. Her aesthetics are complete nonsense compared to her backstory.
also correct me if im wrong but doesnt karthus Q bubbles scream or moan or something along those lines? That could be considered singing with how often he uses that ability
nothing angelic about her, her sister atleast binds you like a demon would
identity is so weak i didn't even notice they change him form being some random sea creature from " Atlantis " to a yordle, plus there is nothing "tricky" about his kit 90% of the time. fizz jumps on you and runs, its not like LB where there is a lot of room for error and outplay after that point as a majority of the time its down to if i have E back up unlike LB who's passive gives me time to stall and play around to actually trick people
suppose to be a fighting champion similar to jax. but his whole kit scream pseudo assassin. his lore is obviously based around son goku, but we see nothing of his staff being used except in Q and R and the nimbus is barely visible in his E. does wu exhibit the things son goku can do. yes, but none of them feel impact or meaningful, change out the animations and you wouldn't even know. you cannot same the for someone like 
who looks and feels like a juggernaut at all times
Karthus doesn't have thematic and gameplay problems. Let me try to explain:
Karthus' singing has never been literal. When Riot talks about Karthus "singing", they don't specifically mean that Karthus sings songs to kill people. "Singing" here refers to the singing of a church choir, or the chanting of a priest. In Karthus' case, it also references his status as a wizard, who recites incantations to kill things. Karthus' "song" shouldn't be understood using the standard meaning of the word; it's essentially his speaking mixed with the screaming of tens of thousands of enslaved souls - there's no lyrics, rhyming or music involved. Obviously, his requiem is a spell and not a musical composition.
Karthus' singing has never been his main theme. Karthus has always been a powerful spellcaster who wanted eternal life and raised undead legions to do his bidding. In the old lore, Karthus ruled over a swamp full of skeletons and zombies and killed everyone who entered his kingdom. In the new lore, Karthus manipulates the Black Mist and sends the Fallen across Runeterra to kill and raise more undead.
His gameplay is balanced, iconic and unique. It doesn't go against his lore. Karthus knows that his magic is painful. He says so in his quote: "Pain is the herald of your salvation.". He doesn't want his victims to suffer, but knows that there's no other way to free them from their flesh. He tears Vionax's soul out of her body, he threatens to burn and shred living beings, and even his selection quote mentions the beauty of an agonizing death.
TL;DR: Karthus is well-written and thematically cohesive.
There's a couple but I'm gonna say 
. In the lore, a personification of death divided in two, who each hunt different kinds of people depending on whether the victim accepts death or runs from it. Q is really boring and could be on any adc kit in the whole game. W is the most boring imaginable way to have Wolf be a particle effect. An execute would be more fitting on this champ than any other and yet they don't have one... instead they have a no death zone. Why? They are DEATH, why are they choosing to just not kill now?? And then a heal?
Karthus is a lich from the Shadow Isles, a land full of dark magic. That would probably explain his abilities. His ult is his song.
Like, what a champion is suppose to be, having no correlation to their character, their design, and/or their kit.
I think that honor goes to
He is suppose to go around singing, and adding the spirits of anyone who he has written into his book into his ghostly choir. He doesn't do any of that. Like, outside of his passive, his entire kit could belong on any generic spell caster.
You haven't seen what Gragas and his pre-retcon lore looked like
This champion not only has a nonsense skillset, but also a abhuman proportion, and used to have a absolutely ridiculous lore that explained about it, and I thought the riot lore staff was trolling the whole community.
"Gragas used to go in taverns and go brawling until he was banned from every tavern near Noxus because he was a AWFUL customer even in "pre-retcon everyone is evil" NOXUS standards. Then he decided to make his own drink because nobody allows him to enter their store. BUT lo and behold! The drink he made was contaminated by RUNE WAR RADIATION AND SHIET that he became massive like villains in fallout or Fist of the North Star. Also his drinks became also poisonous and explosive as well for whatever reason.
WTF is this dribble.
As much as I love Garen's ult I find it kind of weird. Because Demacia is anti-magic right? So why does Garen have this giant sword summoned from the sky? Never really made sense if you ask me. They even included it in the cinematic. Would make more sense if he had something similar to 
