Scariest Champ When Played Well

For me, the the scariest champs in the game when played by someone experienced with them are the following:

Shaco: A good Shaco can get an easy first blood at the enemy jungler's red, pull off terrifyingly effective ganks, essentially win the game for his team by 10 minutes, and generally cause chaos. Zed: Although Zed has a lot of counter play, a good Zed can melt carries and do a massive volume of damage without getting touched, provided that this good Zed is skilled at manipulating his shadows. Mordekaiser: A good Morde can double his lane opponent's cs, while being able to tank a ton of damage with his passive shield. Once he gets Rylai's and Will of the Ancients, a good Mordekaiser is pretty much untouchable. Hue. Syndra: Where did all your health go? Oh yeah, an experienced Syndra just wiped half of it in a single burst. Ouch. Diana: Though Akali is often credited as the most ridiculously powerful AP assassin in the game, a good Diana is a nightmare when she hits level 6. A single combo can tear right through a carry by 20 minutes in, even if Diana falls behind.