thermonuclear FORTRAN
Approximately 11000 lines, all screaming capitals, no indentation. Of course no subroutines! About a hundred magic numbers, The program had 1 (one) comment in total, midway in, after a goto jumping almost 1000 lines forward. The comment read: "not needed".
I warned the poor guy supposed to polish this monstrosity that he'd have a "window job": if you try this, you'll jump out of a window in despair. He left after spending eight weeks of trying with exactly zero progress. I was glad he did, as he looked unhappier every week and very much like a zombie near the end.
Beat this.
Biting the hand that feeds IT
