Everyone in the Steam forums is being really whiny about this achievement and swapping game saves to get their ticket. I'm kind of a little bitter about that.
I'm not even that good at this game, I don't think, and still managed to do it. The Kid can get you way under par on those moving platform levels. Beh.
Honestly, I think the hardest part was beating Billy Boy, which I for whatever reason find insanely difficult.