No such thing.
I personally thought Double science and Maths were the easiest things ever and that English was kinda hard, and alot of people would think me mad for thinking Maths is easy and they get infuriated by it.
Depends what you like.
Oh and all of them are sooo easy. Don't go to university if you don't find them a breeze.
GCSES: easy
AS level: still easy but jump from GCSE
A level: a jump from AS but still fairly easy if you're passionate for the subject, moderate if you don't
University: challenging
Post grad: O shi- you better love your subject a whole lot