What is the scariest one trick champion?

Hello everyone!

I have picked up League of Legends after a long break and I am enjoying this game! This time, a friend of mine who has never played league before started playing it and I am helping him as much as I can.

We had a conversation about the number of champions in the game and what champions are "stronger" than the others.

So what do you guys think is the scariest one trick champion when played at the absolute perfect level? My vote probably goes to Riven because of the skill level needed to play her at a good level.

Thank you in advance.