Kensuke Hamada has made what I think is the 4th ascent of Tokio Muroi's Bansousha at Ogawayama, Japan. Weighing in around 8B(ish), this if one of the most difficult slab boulders in the world, if not THE most difficult. I've no idea. (If you ask me, all slabs are heinous, so let's not go there).
According to a comment below, Tokio climbed a possibly even harder slab, Kakusei (??), just to the right of Bansousha (the "line" just behind Nalle), in December 2007. This ungraded problem has yet to be repeated.