Of all dei ex machina, one of the laziest is inventing a single point of failure
that allows an overwhelming adversary to be taken out by a small attack.
For example, in Enterprise S3, there is this network of thousands of enormous spheres that is making the Delphic Expanse dangerous for its inhabitants. What can anybody do about that? Then we’re told in the last two episodes of the season that attacking a single point on a single sphere can destroy all the spheres.
In FC, the Borg have overrun the Enterprise. How can they possibly be beaten back? No problem, just kill the Queen and they all die. Similarly, the Cube in the first act was destroyed by focusing the entire attack on a single point, which was explicitly ruled out in BOBW.
Note that a single point of failure doesn’t have to be a deus ex machina if it’s properly set up. For example, the Death Star in Star Wars is taken out by a pair of proton torpedos, but this was set up from the beginning of the movie. The whole story is motivated by the idea that the information stored in R2D2 might identify such a vulnerability in the Death Star.
So, what are some of the worst SPOF DEMs in Trek?