Given that Dr. Culber says that Su'Kal will no longer be dangerous once he leaves the dilithium planet, I get the impression that you need a massive amount of dilithium to be able to broadcast powerful enough waves into subspace to cause another Burn.
SU'KAL: What if it [the Burn] happens again?
DR. CULBER: It won't. Not once we take you from here [the dilithium planet]
So the only way the Federation's enemies would be able to create another Burn is either a) capture the dilithium planet in the Verubin Nebula, or b) amass a similar amount of dilithium themselves. Also, from what we've seen, the Burn was omnidirectional, so any enemy who tried this would have to not be dependent on dilithium themselves.