So, I was re-watching 'Fantastic Beasts and The Crimes Of Grindelwald,' and I came up with this theory about the blood pact (of doom), I theorized that Dumbledore will be able to fight Grindelwald because the blood pact was phony. I believe that the pact has a fatal flaw to it, it was not created with true love on both sides. I believe that although Dumbledore did it with love on his side, but Grindelwald did it as a way to ensure that his biggest threat could be neutralized. When Grindelwald found out that the blood pact could not protect him, he set out to find Credence Barebone, his only hope to eradicate Dumbledore, that is why he let Newt's Niffler steal the pact, he had no need of it any longer.

How do you like this theory, please comment any flaws or addition in this theory.