If Blackbeard awakens one of his Devil Fruit powers, the only character who could defeat him in One Piece would be Trafalgar D. Law.
Law vs Blackbeard Fight (1093 ep) Full fight Awakened Law Vs Blackbeard
The biggest threat in the One Piece world, Marshall D. Teach, popularly known as Blackbeard, has become an even bigger threat ever since he defeated Trafalgar D. Law. After beating Law, he has obtained the prints of two Road Poneglyphs, making him the second best contender for the One Piece treasure after Luffy.
Not only does he have access to two of the strongest Devil Fruit abilities, but if he manages to awaken even one of them, he would be in a completely different league. His awakening would make him the worst villain in the One Piece story. Although it has not been confirmed, given his importance as an antagonistic character, there is a high chance that it could happen.
Blackbeard's awakening would be the greatest threat, and the only person who could counter or even triumph over his Devil Fruit awakening is his former adversary Trafalgar Law. Law has a specific ability that can help him take down Blackbeard once and for all.
