For the Haters
Heaviest home defeat: Bayer Leverkusen's heaviest home defeat (as of December 2019) came in one of the many Rhineland derbies. On February 14, 1981, Bayer 04 lost 1-5 to Borussia Mönchengladbach. On January 21, 1984, Bayern triumphed by the same score at the Ulrich-Haberland-Stadion. The disastrous 3-6 against Bayern on August 29, 2009 added further humiliation.
Heaviest away defeat: The heaviest away defeat came against Borussia Dortmund — not in the Bundesliga, but in the 2. Bundesliga Nord. In the 1975/76 season, BVB thrashed Bayer 04 Leverkusen 7-0 on matchday 12.
Longest losing streak: The longest losing streak came in the 2002/03 season. The Werkself lost five consecutive matches from matchday 17 to 21.
Most defeats per season: The record for most defeats in a season was set twice. Bayer Leverkusen lost 18 matches both in the 1975/76 second-division season and in the 1981/82 Bundesliga campaign.
Most consecutive matches without a win: This negative record was also set twice. The Farbenstädter went 13 matches without a win both in 1980/81 and in 1995/96.
Most embarrassing cup turnaround: The most embarrassing cup turnaround for Bayer 04 was delivered by Michael Ballack and co. in Dresden in 2011. The newly promoted second-division side overturned a 3-0 Leverkusen lead in just 22 minutes to make it 3-3, and three minutes before the end of extra time, the Rudolf-Harbig-Stadion erupted as Dynamo made it 4-3. Leverkusen were humiliated.
Nothing to correct about the biggest international debacle: a 2-10 aggregate in the 2011/12 Champions League round of 16 against FC Barcelona. In a Champions League group stage, the 0-5 against Manchester United on November 27, 2013 represented the heaviest international defeat. In the Bundesliga, the Werkself were never more embarrassingly beaten than the 1-6 at newly promoted Hannover 96.
Five-point lead squandered in two matches: The 2001/02 season saw Bayer Leverkusen effectively crowned champions with three matchdays remaining. Five points clear of Borussia Dortmund — what could go wrong? In short: just about everything. A complacent home performance against Werder Bremen (1-2) with a missed penalty from keeper Hans-Jörg Butt, followed by further dropped points, handed the title to Dortmund.
Unterhaching — Schwarz creates distance: If anyone researches the origin of the term "Vizekusen," they will find answers on May 20, 2000. Three points clear of Bayern but with an inferior goal difference, Bayer Leverkusen went into their final match at newcomers SpVgg Unterhaching. After the 4-1 on matchday 33 against Eintracht Frankfurt, Bayer coach Christoph Daum had cranked up the pressure — only for the team to collapse at the decisive moment.