What was BVB's best victory?

BVB received its best home match score against Arminia Bielefeld 11-1 on 6 November 1982.
Borussia Dortmund played 7-0 three times: against Schalke 04 in 1965/66 season, against HSV in 1966/67 season and against Blau-Weiß Berlin in 1986/87 season.
Best away victory dates back from the 1994/95 season (6-1 against 1.FC Cologne).
But Borussia celebrated the best score in a compulsory match against BSV Schwenningen in the first round of the DFB cup championships 1978/79: 14-1!
BVB's best international victory is an 8-0 over Floriana La Valetta (Malta) during European club champions' cup tournament in 1965/66.

Which were BVB's biggest successes?

A list of BVB's successes and other special honours of BVB players can be found on Borussia Dortmund's web pages in the category BVB - Successes