This is not list you vote for:
Thanks for your time
-CatPlayInGuitar
To me, the scariest skins are the Dragon Slayers...
... like... dude... they are wearring my father as armor... that is gross and scary.
These are the most scary or dark champions lore/visually wise in my opinion:
For the scariest skins (not counting legacy or event skins here) i would maybe say:
Spooky 
, Bittersweet 
, Sewn Chaos , Giant Enemy Crabgot 
, any Skins, Armor of the fifth age 
(still love it <3) and Nightmare 
.
Well there aren't many too scary things in league. The only "real" scary things are when you play ADC against a Rengar in the middle of the night and you just get a heartattack because he jumps from the most ridiculous spot (mostly from some bush) onto you or seeing the Nocturne ult for the first time.
butcher urgoth
is in my opinion the scariest champion.
I mean the other champs might kill you,but most of them wouldn't bother to torture you. But thresh,he would drive you mad,torture you to death,then capture your soul and then torture you for all eternity....
In my opinion, Kindred is one of the scariest. You can't run from death or you'll have your soul devoured. And if you accept it, you're consenting to giving up everything you know and love. The idea that there's a being out there that would hunt you until you're no more is quite intimidating.
People are actually scared of LoL champions?
Blackfrost anivia is quite terrifying if you think about the implications her existence represents for the freljord.
Anivia is quite literally the embodiment of the Freljord. To have her and therefore the entire landscape corrupted (perhaps at the same time) because of the watcher's return is very, very bad juju.
Whatever the watchers were in the time of Lissandra and Avarosa...they'll no longer play nice, if they were nice in the first place.
Sion.
Can you imagine meeting that monster on the battlefield? Taking the souls of the dead and refusing to die as he comes toward you?
That fucker is terrifying.
His ultimate essentially makes the world round you your own nightmare, as seen in the Twist of Fate cinematic with Ryze.
My scariest experience in league was fighting my first Rek'Sai - I heard that ult scream and nearly pissed myself. It was also fed too, so when it attacked me, I got permastunned and died so fast I had no idea what was going on.
The only champions who gave me the creeps in sense of "horror feeling" are and 
The former because of what he is, his old lore and the fact that we don't know anything about him....
The latter reveal (the lamb&wolf story) got me hyped and shivers.
I'm pretty sure it would be terrifying to be on the bad side of 
Being an Ascendant means he's one of the strongest beings in the entire world. He is actually so strong that one of the tips on the Client says that when his Ultimate is up he's stronger than most champions in the league.
Then there's his Infernal skin, which requires no explanation as to why it is the scariest thing in the game.
Also here's Blood Moon Kennen's splash art, if you haven't seen it yet: https://1.bp.blogspot.com/-er9Um0E03Mw/VsUL8aRuDlI/AAAAAAAA4E0/7OxBm9tEhnM/s1600/Kennen_Splash_6.jpg
I think the shadow Isle part is the most scariest one. Death is just the beginning of an endless torment..
