I'm curious.
For me it was the Teutonic Knight base. I was so weak that I had to kill them one by one and even then it was only luck if I got the first hits in. So many reloads; it was driving me insane. At one point I was down to Erik and Serena, with no way to resurrect Christof and Wilhem, and every fight slaughtered us. Couldn't get my gear back, because there were 5 knights in the room with it who annihilated us if we tried, so we were half naked as well. Took me several hours to get past one floor. DX Not counting the copious bugs where someone got stuck in a corner or at the bottom of the stairs.