The Curse of a Brahma Jnani

The curse of a Brahma Jnani is indeed very powerful. When the Lord wishes to destroy something that is under His own protection, He accomplishes it only by means of a curse from the mouth of a Brahma Jnani.
The Yadava dynasty was under the protection of Lord Krishna Himself. Yet when He desired to wind up His lila on the Earth and destroy the Yadu Kula, He accomplished it by means of a curse (on Samba, the son of Jambavati) by Brahma Rishis.