User blog comment:BerryBandit/Mechanically demanding champions/Quick decision champions/@comment-5150542-20130622185541

From hardest to well, still hard.

1. Zed

2.Lee Sin

3.Katarina

4.Leblanc

5.Vayne

6.Orianna

7.Fizz

Thresh is close to being hard, but his pro-ness is mostly determined by his team communication skills.

IMO Zed is the hardest one to master, perfect positioning, outplaying, CDR, and all around damage output are needed to make him good.