I am thinking primarily of Star Trek stuff here, mostly just because that is what I am most familiar with. Anyway, the inconsistency in villainy from episode to episode annoys me. Like these really devastating weapons will be invented in an episode, and then they'll never be used again. If you could destroy a planet by sending a certain type of bomb into its star, then why don't these ruthless races or empires do this to conquer their enemies? Why do they instead think it preferable to lose thousands of ships, millions of lives, and tons of resources, waging an ongoing war? Or, another example, if you can use a probe with a bomb to fly around in space outside a ship or space station, identify a target, then blow the window(s) apart, sucking the target into space and killing them, why doesn't this happen more often? Or, another example, there was an episode where a phaser rifle was created that had a scope that could see into other rooms, and when "fired" quickly transported the discharged energy projectile (or whatever term is correct) into the room of the target, thereby killing the target, with little chance of the killer getting caught. Seems like a great way to take out a Sisko or Picard or whoever if you are a Dominion/Cardassian/whatever soldier.
Galactic Geneva Convention?