Conqueror and the champs that use it.
So I've put in about 200 matches roughly into preseason now and this is what I have to say. (This is my opinion, don't take offence too it too harshly, it's what I've experienced.)
So I've been playing practically every role to see how and where they sit.
Top lane: Top lane at the moment is just unplayable, the tank meta is disgusting, practically every single tank in the game is building conqueror and isn't dying. Any bruiser or any mage that tries to kill these tanks practically die by the time the tank reaches half health. I've seen a Urgot 1v5 an entire team without a SINGLE damage item and he had build full tank take down an entire team without him dying. Conqueror is so broken that it just heals you so goddamn much for no reason. This goes for Singed, Mordekaiser, Tahm Kench.Garen. They all basically build all tank and still dish out HUGE amounts of damage without remotely building tank.
Jungle: Jungle at the moment is 50/50, it's to the point where junglers can be anyone, I've seen a Ryze jungle, I've seen Nasus jungle, I've seen a Jhin jungle and they all worked out. At the moment jungle kinda just relies on not dying and ganking botlane a ton. They have to focus dragon way more just to try and get that soul to end the match.
Mid lane: Midlane is basically, pick an assassin and you're trolling. Every GODDAMN mage in this game is busted to shit and after one item can basically one shot you. Kassadin is incredibly strong at the moment considering his ult is a flash with damage, and ryze is stupid strong. Mages are all I have to say.
Botlane: Botlane at the moment is disgusting. Riot has released 2 champs that are botlaners in the last like 2 months and it's just been hell down there. Senna is disgusting on how much poke damage she has and how much damage she can dish out with one ability. Her healing is way too high and her passive is just way too overloaded. She was nerfed this patch but she is still one of the STRONGEST adc's in the game, even if RIOT said "She is not an adc and wont be able to be played adc". Aphelios is just a metal rod shoved up our asses by riot. It's actually mind blowing how this champion got out of the PBE, he has so much sustain and remote damage for just being an adc. I've seen Aphelios just one shot entire team because of his ult. It's disgusting, he doesnt even have to do anything and press r and it does the damage for him. He just MELTS people and just makes you his bitch. His nerfs were a joke and literally did nothing to him. The only reason he isn't up in the charts for his winrate is players still not knowing how to properly combo with him. But once you learn to combo with him it's just insane what he can do.
All and all, I JUST wish that riot would listen and revert conqueror, think before releasing a champ to live servers, and listen to our feedback. Like at the moment there isn't enough bans for the amount of broken champs there is. Like the game legit just hangs on which team can get the most broken champs in the game. Singed legit is super tanky early game and just heals because of conqueror while walking around. Like why is that a thing???
Tl;dr Riot needs to revert conqueror and nerf tanks and mages, remove or fix aphelios and nerf the fuck out of senna and aphelios.