Diminishing Threat Syndrome
A common failing of comic books and action movies where the first time a creature is introduced, it is extremely difficult to defeat. It is often presented as undefeatable except by extraordinary effort and/or luck. However, as the story progresses, more and more creatures of that type are included in the plot, and the more there are, the easier they become to kill.
which bad guy don't you think this has happened to yet? Besides Doom obviously.
I was thinking less about individual bad guys and more about groups. For example, in the beginning of a 3 issue story arc, the X-Men encounter a single Sentinel. It informs them that it is a new model and it has ways to counteract all of their powers. Working together, they barely survive the battle by knocking it into a nearby volcano. But by half-way through the second issue, the X-Men are tearing through a Sentinel base, and Cyclops is singlehandedly blasting off their heads three at a time.
Reference from SuperMegaMonkey : chronocomicThe X-Men then raid the space station. The Sentinels in these stories suffer from Diminishing Threat Syndrome. It is explained that Lang's Mark III Sentinels are not as sturdy as the Trask originals, but that doesn't explain why the first few that attack in Manhattan were so tough. Read More: Uncanny X-Men #98-101
Reference from SuperMegaMonkey : chronocomicThe Dreadnoughts suffer from a bit of Diminishing Threat Syndrome... Read More: Iron Man #138-139
Reference from SuperMegaMonkey : chronocomicRecall that the first time the FF encountered this android, it was so powerful that they could not stop it - they could only throw it into the Negative Zone. Now that it's returned, in possession of the Cosmic Control Rod, the FF defeat it in a few panels. That's the definition of Diminishing Threat Syndrome. Unless you want to argue that Tigra somehow tipped the scales. Read More: Fantastic Four #183