For reall who is the most difficult champion?
Because it is definitely not Aphelios.
Because it is definitely not Aphelios.
Kalista.
Partly because her stats are extremely weak to accommodate her kit which gets extremely strong for two well coordinated players. Also because her passive is similarly powerful with high mechanical skills.
Ivern
You can say others are more complicated, yes that is very true. However, his very concept is difficult. Trying to compete against powerful junglers as a shielder support. In terms of difficulty, you are in for a rough ride.
Garen

I like to say that it is Kalista. You have my respect if you can properly play her.

not hardest to play but hardest to play optimally
She requires you to excel at animation canceling almost constantly against both minions and champions while focusing on your fights and the map. I don't think a single player in the entirety of league has really mastered her due to some of her cancels being so timing sensitive and I've watched a lot of the top Nidalee players play.
As someone that's tried both Nid and Ivern, he requires a different mindset and probably the strongest mental game of any champ in league, but he doesn't go near Nidalee when it comes to mechanical aptitude or even practice required.
As a test if anyone owns her, I've seen the best players clear all 6 camps and get to the scuttle almost as it spawned via animation canceling with no leash and near full HP. Go into a practice match and try that and you'll see what I mean when I say she's not one of, but THE hardest to master.
Few people can play him right.
Most skillshot reliant champion in the game.
I see people saying Kalista, but I remember when she came out and I found that I could win teamfights by buying a Runaan's Hurricane and then shift-clicking on my fountain to perma-kite without even looking at the screen... She may be undertuned now, but she definitely does not have the hardest kit. I think the honor of most challenging kit/playstyle goes to Nidalee or Azir.
I wouldn't say Shsvo is the hardest but he's up there. Kit kit is simple but optimizing it is crazy because there's just so much you can do and so much you need to think ahead about. He's a champion that requires you to not only play well with, but also out-play well on.
Gonna have to say, whatever I am playing at the time. Same goes for champ balance. Any champ I play against is broken and my champ needs buffs. It is known.

Pressing E on your ADC is hard :^)
( I am a support main and reserve the right to poke fun at my own class)
Jokes aside, for me personally, I'd probably say Draven just because of learning how to properly micromanage those darn axes. If you go to Riot's official rating (which is now 1-3 instead of 1-10), some of the most difficult are Kindred, LeBlanc, Ivern (surprisingly), Cass, Azir, ASol, Thresh, Zoe, and more. Some of those listed are easy for me, some are harder, some I don't like so honestly it probably comes down to the player.
- I have no idea how people do well with him. I always get cced, focused down, and end up 0/10 or something. Lately I had a game where I got lucky in the early game, got 4 kills... and I was still useless as fuck.