From what I took, easiest to hardest:
English Lit
Art
Biology
Chemistry
I only find Eng Lit quite easy because I enjoy it so much though. Like, I'd do it in my free time tbh. I imagine it's horrific if you're not interested.
Art is harder than you'd expect because so much effort has to be put in to achieve anything worthwhile, visually and grade wise. Since I was doing two sciences and an essay subject with it, I had to compromise on revision for Lit to get stuff finished to a high enough standard. I didn't have any weekends for a whole year with that and Chem.
Biology (people have mentioned) has a cruel mark scheme, at least, for AQA. It's a lot of material and I spent two months learning the textbook cover to cover, and then my exam had very little breadth of recall and a lot of common sense, and I wasn't very impressed. It's way interesting at A2 though
Chemistry is like being in a relationship where your partner takes your money and your time and leaves you frustrated and hating them, but at the same time, they're so attractive and enigmatic you keep in going, even though you're not sure if the effort you put in will pay off. And at AS results day I found they they paid off just enough to keep me hanging on by a slither of hope. (And of course I mean, a C)