In The Court Of The Crimson King. Apart from 21st Century Schizoid Man & Epitaph it's utter nonsense IMO. All their other albums (up to Thrak) I can (& do) segue up & cheerfully OD on, but not 'Court'.
Blue Oyster Cult. The three studio albums before Agents of Fortune are, in the main, quirky, angular slices of serious goodness, but AoF is just FM Rock dross.