1-5 against Borussia Mönchengladbach: the biggest derby humiliation against Gladbach came on 14 November 1984. On a Wednesday night in Müngersdorf, goals from Hans-Georg “Schorsch” Dreßen, Frank Mill, a brace from Uwe Rahn and one from Hans-Günter Bruns gave the Foals a 5-1 win. Nothing worked for Köln that day. Stephan Engels and Klaus Allofs even missed penalties within eight minutes of each other against Gladbach goalkeeping legend Uli Sude.
It was already 4-0 at half-time.