Hmmm...before I'm comfortable saying it's the hardest 3b box ever, I'd have to all of Murakami's relatively recent videos.
I can't think of any off-hand that are harder. A cross-2xed inverted box and an inverted box with the 2x behind the head are both tough variations I've seen done, but I don't think that either of them are in the same league as HLAIB.
by Mike Moore, in response to this post 2015-09-11 15:03:31