There was a time when the spanish press dubbed Bayern "La Bestia Negra del Madrid" (meaning, Madrid's Black Beast... Black Beast being a popular term in Spain for an unbeatable nemesis), and this was when Bayern would consistently knock out Madrid in HIGHLY DISPUTED ties which would often come down to the away goal tiebreaker or penalty shootouts.
Now, considering how Madrid has been consistently keeping the bavarians in their pocket over the last decade, and how Bayern has been stomping Barcelona with such ruthlessness, we can definitelye say that Bayern has become Barça's Bestia Negra, and has taken it to a whole new level.