Two of the bad ends on the Near Side route, scenes 512 and 513. Mirror Moon translated it as "Shakes 'n Shivers Animal Land".
The first one is the land shark, you've seen it, everybody's fucking seen it, because splitting up in a horror movie situation is stupid.
The second one was mentioned on the PLUS-DISC as being the hardest scene to reach. Even the scenario director couldn't get to it without a flowchart. You need to end up with more Ciel points than Arc points when Nero attacks the hotel, but WITHOUT having been in Ciel's apartment (which is what puts you on her route).