I wanna say this is the basis of one of the paperback books I had as a kid, couldn't tell you the name. But basically someone coopts the Doomsday machine, I think its an El-Aurian, as revenge for the Borg assimilating their people. And then they basically go on a Borg destroying rampage?
I also read this in the first encounter it mentions a sentence like, "the planet killers anti proton beam laughed at the Borg shields..." And that really caught my attention as a child when the Borg seemed nearly impossible to beat.