The phrase "biggest idiot" is used to describe someone who is extremely foolish or unintelligent. It emphasizes that the person being referred to is the most foolish among all others. Full definition
We are at a point where no f00ks are being given, those fans who attend the matches are biggest idiots in london i say, you must be some kind of special stupid to not understand, that to hurt the current board is by not attending the matches ---- Arsenal fc, The club with most moronic fans the world has ever seen (justarsenal.com)
The problem with you dumbfuckers is that «Pastor Dave» is just as big an idiot as you are. (religion.blogs.cnn.com)