Iker and Eneko Pou has put up what could very well be the most difficult multi-pitch on the planet, the 500m Orbayu. With a hardest pitch of 8c+/9a it's probably the hardest bigwall ever climbed. Maurizio "Manolo" Zanolla, also mentioned in the post below, climbed Solo per vecchi guerrieri, 8c/9a, a couple of years back, but I guess it doesn't qualify as a proper bigwall. Also, didn't a couple of British guys, James MacHaffie and someone climb an 8c+ slabby multi-pitch on Madagascar (Tough enough?)a year or so back? I'll check on that later, when I've got time.