For those who have watched the newly released Fantastic Beasts: The Crimes of Grindelwald, you will find a "bloodpact" (which is something very similar to the Unbreakable Vow) mentioned there between Dumbledore and Grindelwald where they swear to not fight each other ever.
However, we know from the Harry Potter and Deathly Hallows book that Grindelwald and the two Dumbledore brothers had fought which led ultimately to the death of Ariana Dumbledore:
And then ... you know what happened. Reality returned, in the form of my rough, unlettered, and infinitely more admirable brother. I did not want to hear the truths he shouted at me. I did not want to hear that I could not set forth to seek Hallows with a fragile and unstable sister in tow. ‘The argument became a fight. Grindelwald lost control. That which I had always sensed in him, though I pretended not to, now sprang into terrible being. And Ariana ... after all my mother’s care and caution ... lay dead upon the floor.’ (Harry Potter and the Deathly Hallows, Chapter 35, "King's Cross")
Needless to say, this event occurs in 1899, long before 1927, the year Crimes of Grindelwald is set. Now obviously this bloodpact was made between the two before Ariana's death because Grindelwald fled right after her death. So shouldn't have either of the two individuals or even both died for having violated this pact?